U.S. patent number 8,875,969 [Application Number 11/774,943] was granted by the patent office on 2014-11-04 for fastener driving apparatus.
This patent grant is currently assigned to Tricord Solutions, Inc.. The grantee listed for this patent is Christopher Pedicini, John Witzigreuter. Invention is credited to Christopher Pedicini, John Witzigreuter.
United States Patent |
8,875,969 |
Pedicini , et al. |
November 4, 2014 |
Fastener driving apparatus
Abstract
A fastener driving apparatus for driving fasteners into a
substrate. The fastener driving apparatus is a combination of a
motor driven linear motion converter; a compression cylinder; an
expansion cylinder and a valve arrangement. The linear motion
converter converts a rotational motion of a motor to a linear
motion of a compression piston within the compression cylinder
causing a gas within the compression cylinder to be compressed. The
compressed gas is communicated to the expansion cylinder through
the valve arrangement wherein the compressed gas expands causing an
anvil coupled to an expansion piston within the expansion cylinder
to move axially. The axial movement of the anvil causes a fastener
to be driven into the substrate. The fastener driving apparatus is
an ergonomically designed portable hand held tool providing comfort
to a user, meeting safety standards and performance efficiency
requirements.
Inventors: |
Pedicini; Christopher
(Nashville, TN), Witzigreuter; John (Canton, GA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Pedicini; Christopher
Witzigreuter; John |
Nashville
Canton |
TN
GA |
US
US |
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Assignee: |
Tricord Solutions, Inc.
(Nashville, TN)
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Family
ID: |
39684991 |
Appl.
No.: |
11/774,943 |
Filed: |
July 9, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080190988 A1 |
Aug 14, 2008 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60906120 |
Mar 9, 2007 |
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60900480 |
Feb 9, 2007 |
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Current U.S.
Class: |
227/130; 227/131;
227/8; 227/10 |
Current CPC
Class: |
B25C
1/04 (20130101); B25C 1/06 (20130101); F16K
15/02 (20130101); Y10T 137/7929 (20150401) |
Current International
Class: |
B25C
1/04 (20060101); F16K 15/02 (20060101) |
Field of
Search: |
;227/8,10,130,131
;173/2,11,39,207,114,48,200 ;123/46H,46A ;417/520 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lopez; Michelle
Attorney, Agent or Firm: Aldenbaum Schloff and Bloom PLLC
Schloff; Jay
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
The present invention claims priority under 35 United States Code,
Section 119 on the provisional application No. 60/906,120 filed on
Mar. 9, 2007 and the provisional application No. 60/900,480 filed
on Feb. 9, 2007.
Claims
We claim:
1. A fastener driving apparatus, comprising: a power source; a
motor electrically connected to the power source; a first cylinder
comprising a first piston reciprocally movable within the first
cylinder, the first piston defining a gas chamber within the first
cylinder, the gas chamber capable of accommodating gas therein; a
first cylinder end cap configured at a first end of the first
cylinder, the first cylinder end cap configuring the gas chamber
between the cylinder guide, the first piston and the first cylinder
end cap, the first cylinder end cap having a hollow portion, a
slider crank arrangement driven by the motor, the slider crank
arrangement operationally coupled to the first piston and
configured to cause the first piston to reciprocally move within
the first cylinder; a second cylinder comprising a cylinder guide,
a second piston disposed within the cylinder guide, the second
piston having a front face and a rear face, and an anvil coupled to
the rear face of the second piston, wherein the second piston is
capable of linearly moving within the cylinder guide, thereby
enabling the anvil to move in a driving direction; and a valve
arrangement operationally disposed between the first cylinder and
the second cylinder, the valve arrangement defining a gas
passageway for communicating the gas from the first cylinder to the
second cylinder and the valve arrangement capable of assuming one
of an open position and a closed position; wherein the gas received
within the gas chamber is compressed by the first piston in a
single stroke of the slider crank arrangement in a manner such that
the compressed gas is communicated into the second cylinder through
the gas passageway of the valve arrangement, causing the compressed
gas to expand in the second cylinder thereby causing the second
piston to move linearly and enabling the anvil to drive a fastener
into a substrate in the driving direction in the single stroke of
the slider crank arrangement.
2. The fastener driving apparatus of claim 1, wherein the slider
crank arrangement is driven by the motor through a reduction
mechanism.
3. The fastener driving apparatus of claim 1, wherein the first
cylinder further comprises a cylinder guide configured to dispose
the first piston there within, and a check valve, such that in an
open position the check valve enables the entry of gas into the gas
chamber and in a closed position prevents exit of gas from the gas
chamber.
4. The fastener driving apparatus of claim 1, wherein the gas
compressed by the first piston achieves a pressure consistent with
a compression exponent equal to or greater than 1.05 before the
valve opens.
5. The fastener driving apparatus of claim 1, wherein the valve
arrangement comprises a valve body having a groove, a valve spool
disposed within the groove, the valve spool having a front face
portion, a rear face portion, and a valve spool stem extending
outwardly from the front face portion, a valve return spring
disposed within the groove and towards a rear end portion of the
groove, and a gas passageway extending from the groove to the
second cylinder, the gas passageway configuring a duct for
communicating the gas from the gas chamber of the first cylinder to
the second cylinder.
6. The fastener driving apparatus of claim 5, wherein the valve is
mechanically tripped by a single stroke of the first piston by at
least one of an electric motor, an electric signal, the first
piston, and a cam.
7. The fastener driving apparatus of claim 5, wherein a closed
position of the valve arrangement comprises the valve spool being
disposed in the hollow portion of the first cylinder end cap, the
valve spool stem extending into the gas chamber, and the valve
spool closing the gas passageway.
8. The fastener driving apparatus of claim 5, wherein the volume of
the gas passageway is less than 15% of the gas chamber volume in
the first cylinder.
9. The fastener driving apparatus of claim 5, wherein the valve
arrangement is a snap acting valve and the valve spool has an
opening time of less than or equal to about 20 milliseconds for
opening from the initial closed position to greater than or equal
to about 70 percent of full flow of the compressed gas.
10. The fastener driving apparatus of claim 1, wherein the second
cylinder further comprises an anvil drive bumper configured at an
end of the second cylinder away from an end coupling the valve
arrangement, and an anvil retracting mechanism configured to
retract the second piston to an original position.
11. The fastener driving apparatus of claim 10, wherein the
original position is the position of the second piston towards an
end of the second cylinder coupling the valve arrangement, and
wherein the anvil retracting mechanism is in a substantially
relaxed state.
12. The fastener driving apparatus of claim 1, further comprising a
clutch configured to allow the motor to run continuously and
enables storing energy necessary to drive the fastener into the
substrate in the motor before being transferred to the slider crank
arrangement.
13. The fastener driving apparatus of claim 1, further comprising
at least one sensor configured to sense and locate the positions of
the first piston within the first cylinder during the single stroke
of the slider crank arrangement.
14. A fastener driving apparatus comprising: a power source; a
motor electrically connected to the power source; a first cylinder
comprising a first piston reciprocally movable within the first
cylinder, the first piston defining a gas chamber within the first
cylinder, the gas chamber capable of accommodating gas therein; a
first cylinder end cap configured at a first end of the first
cylinder, the first cylinder end cap configuring the gas chamber
between the cylinder guide, the first piston and the first cylinder
end cap, the first cylinder end cap having a hollow portion, a
linear motion converter driven by the motor, the linear motion
converter operationally coupled to the first piston and configured
to cause the first piston to reciprocally move within the first
cylinder; a second cylinder comprising a cylinder guide, a second
piston disposed within the cylinder guide, the second piston having
a front face and a rear face, and an anvil coupled to the rear face
of the second piston, wherein the second piston is capable of
linearly moving within the cylinder guide, thereby enabling the
anvil to move in a driving direction; and a valve arrangement
operationally disposed between the first cylinder and the second
cylinder, the valve arrangement defining a gas passageway for
communicating the gas from the first cylinder to the second
cylinder and the valve arrangement capable of assuming one of an
open position and a closed position; wherein the gas received
within the gas chamber is compressed by the first piston in a
single stroke of the linear motion converter in a manner such that
the compressed gas is communicated into the second cylinder through
the gas passageway of the valve arrangement, causing the compressed
gas to expand in the second cylinder thereby causing the second
piston to move linearly and enabling the anvil to drive a fastener
into a substrate in the driving direction in the single stroke of
the linear motion converter.
15. The fastener driving apparatus of claim 14, wherein the linear
motion converter is one of an eccentric, a cam, a rack and pinion
arrangement, a slider crank, a four-bar linkage, and a lead
screw.
16. The fastener driving apparatus of claim 15, wherein the linear
motion converter is driven by the motor through a gear reduction
mechanism.
17. The fastener driving apparatus of claim 14, wherein the first
cylinder further comprises a cylinder guide configured to dispose
the first piston there within, and a check valve.
18. The fastener driving apparatus of claim 14, wherein the valve
arrangement comprises a valve body having a groove, a valve spool
disposed within the groove, the valve spool having a front face
portion, a rear face portion, and a valve spool stem extending
outwardly from the front face portion, a valve return spring
disposed within the groove and towards a rear end portion of the
groove, and a gas passageway extending from the groove to the
second cylinder, the gas passageway configuring a duct for
communicating the gas from the gas chamber of the first cylinder to
the second cylinder.
19. The fastener driving apparatus of claim 18, wherein the valve
arrangement is disposed between the first cylinder and the second
cylinder in a manner such that the valve spool is disposed in the
hollow portion of the first cylinder end cap.
20. The fastener driving apparatus of claim 18, wherein a closed
position of the valve arrangement comprises the valve spool being
disposed in the hollow portion of the first cylinder end cap, the
valve spool stem extending into the gas chamber, and the valve
spool closing the gas passageway.
21. The fastener driving apparatus of claim 18, wherein an open
position of the valve arrangement comprises the valve spool moving
linearly within the groove in a manner such that the hollow portion
of the first cylinder end cap and at least a portion of the gas
passageway is open.
22. The fastener driving apparatus of claim 18, wherein the volume
contained in the gas passageway is less than 15% of the first
cylinder gas chamber volume.
23. The fastener driving apparatus of claim 14, wherein the second
cylinder further comprises an anvil drive bumper configured at an
end of the second cylinder away from an end coupling the valve
arrangement, and an anvil retracting mechanism configured to
retract the second piston to an original position.
24. The fastener driving apparatus of claim 23, wherein the
original position is the position of the second piston towards the
end of the second cylinder coupling the valve arrangement and the
anvil retracting mechanism is in a substantially relaxed state.
25. The fastener driving apparatus of claim 14, wherein the valve
arrangement is a snap acting valve and the valve spool has an
opening time of less than or equal to about 20 milliseconds for
opening from the initial closed position to greater than or equal
to about 70 percent of full flow of the compressed gas.
26. The fastener driving apparatus of claim 14, further comprising
a clutch configured to allow the motor to run continuously and
enables storing energy necessary to drive the fastener into the
substrate in the motor before being transferred to the linear
motion converter arrangement.
27. The fastener driving apparatus of claim 14, further comprising
at least one sensor configured to locate the position of the first
piston and enabling the motor to be braked.
Description
FIELD OF THE INVENTION
The present invention relates to fastening mechanisms, and, more
specifically, to fastener driving systems requiring operation as a
portable hand tool.
BACKGROUND OF THE INVENTION
Fastener driving systems (such as fastener drive tools and nail
guns) are common in the construction industry. Fastener driving
systems have many advantages over hammers, such as the ability to
drive a fastener instantly without splitting wood, and consistently
setting a nail head below a substrate. Fastener driving systems are
usually driven by electromagnet(s), compressed air or a small
explosive charge. These power assisted means of driving fasteners
can be either in the form of finishing nail systems used in
baseboards or crown molding in house and household projects, or
alternatively, in the form of common nail systems used to make
walls or hang sheathing onto same. Such fastener driving systems
may either be portable (i.e., not connected or tethered to an air
compressor or wall outlet) or non-portable.
Various concepts and components are conceded and emphasized as
attempts and develops over the years in the art of fastener driving
systems and similar explosively actuated equipment. The most common
fastener driving system uses a source of compressed air to actuate
a cylinder to push the nail into a receiving member. For
applications in which portability is not required, this is a very
functional system and allows rapid delivery of fasteners for quick
assembly. A disadvantage of such a fastener driving system is that
the user is required to purchase an air compressor and associated
air lines in order to use this system. A further disadvantage is
the inconvenience of being tethered through an air hose to an air
compressor.
To solve the problems of fastener driving systems actuated by
compressed air, several types of portable nail guns operable by
fuel cells have been developed. Typically, these guns have a
cylinder in which a fuel is introduced along with oxygen from the
air. The subsequent mixture is ignited with the resulting expansion
of gases pushing the cylinder and thus driving the nail into the
substrate. However, this design is complicated and is more
expensive then a standard pneumatic nail gun. Such fuel cell driven
units also have certain disadvantages: the chambering of an
explosive mixture of fuel; the use of consumable fuel cartridges; a
loud report; and the release of combustion products.
Another commercially available fastener driving system is nail guns
using electrical energy to drive a stapler or wire brad. These
units typically use a solenoid to drive the fastener or a
ratcheting spring system. These units have limited application to
short sized fasteners, are subjected to high reactionary forces on
the user, and are limited in their repetition rate. The high
reactionary force is a consequence of a comparatively long time it
takes to drive the fastener into the substrate. Additionally,
because of the use of mechanical springs or solenoids, the ability
to drive larger fasteners or longer fasteners is severely
restricted, thereby relegating these units to a small niche range
of applications. Further, a disadvantage of the solenoid driven
units is that the above-mentioned unit must be plugged into an
electrical power source in order to have enough voltage to create
the force needed to drive even short fasteners.
Yet another commercially available fastener driving system is a
unit working on a flywheel mechanism and an associated clutch that
interacts with an anvil for driving the fastener. This unit is
capable of driving fasteners very quickly and in a variety of
sizes. The primary drawback to such a unit is the large weight and
size as compared to the pneumatic counterpart. Additionally, the
drive mechanism is very complicated in configuration, thus
requiring a high retail cost in comparison to the pneumatic nail
gun.
Prior art teaches several other techniques of driving a nail or
staple by different fastener driving systems. One of the techniques
is based on a multiple impact design. In this design, a motor or
other power source is connected to the impact anvil through either
a lost motion coupling or other device. This allows the power
source to make multiple impacts on the nail to drive it into the
substrate. The disadvantage in this design is increased operator
fatigue, as the actuation technique is a series of blows rather
than a single drive motion. A further disadvantage is that the
multiple impact design requires the use of an energy absorbing
mechanism once the nail is seated, with such mechanism being needed
to prevent the anvil from causing excessive damage to the substrate
as it seats the fastener. Furthermore, the multiple impact designs
are not efficient because of the constant motion reversal limiting
the operator production speed.
A second technique includes the use of potential energy storage
mechanisms in the form of a mechanical spring. In this technique,
the spring is cocked (or activated) through an electric motor. Once
the spring is sufficiently compressed, the energy is released from
the spring into the anvil (or nail driving piece), thus pushing the
nail into the substrate. There are several drawbacks existing to
this technique. First, this technique comprises a complex system of
compressing and controlling the spring and in order to store
sufficient energy the spring has to be very heavy and bulky.
Second, the spring suffers from fatigue, which gives the tool a
very short life. Furthermore, metal springs have to move a
significant amount of mass in order to decompress, which results
low speed nail drivers that place a high reactionary force on a
user.
U.S. Pat. No. 3,589,588 to Vasku, U.S. Pat. No. 5,503,319 to Lai,
and U.S. Pat. No. 3,172,121 to R. H. Doyle, et al. are the examples
of the use of potential energy storage mechanisms in the form of a
mechanical spring. U.S. Pat. No. 4,215,808 to Sollberger discloses
an improved design, which replaces the mechanical spring with an
air spring, compressing air within a cylinder, and then releasing
the compressed air by use of a gear drive.
Although some of the drawbacks of the above-mentioned technique
using the potential energy storage mechanisms in the form of a
mechanical spring were overcome by the use of air spring, the
application of air spring is subject to other limitations. The
primary drawback is the safety hazard in the event of anvil jamming
on the downward stroke. If the fastener jams or buckles within the
feeder and an operator tries to clear the jam, the operator may be
subjected to the full force of the anvil, as the anvil is
predisposed to the down position. Another disadvantage is the need
to feed the fastener once the anvil clears the fastener on the
backward stroke, which increases the time needed to operate the
device and can result in jams and poor operations, especially with
longer fasteners. A further disadvantage to the air spring results
from the need to have the ratcheting mechanism as part of the anvil
drive. This weight causes significant problems in controlling the
fastener drive since the weight must be stopped at the end of the
stroke. This added mass slows the fastener drive stroke and
increases the reactionary force on the operator.
Additionally, because significant kinetic energy is contained
within the air spring and piston assembly, the unit suffers from
poor efficiency. This technique is also subject to a complicated
drive system for coupling and uncoupling the air spring and ratchet
from the drive train, which increases the production cost and
reduces the system reliability.
U.S. Pat. No. 5,720,423 to Kondo again discloses an air spring
which is compressed and then released to drive the nail. The drive
or compression mechanism used in this technique is limited in
stroke and thus is limited in the amount of energy which can be
stored and introduced into the air stream. In order to get
sufficient energy in the air stream to achieve good performance,
use of a gas supply is provided which preloads the cylinder at a
pressure higher then atmospheric pressure. Furthermore, the
compression mechanism is bulky and complicated. Also, the timing of
the motor is complicated by the small amount of time between the
release of the piston and anvil assembly from the drive mechanism
and its subsequent re-engagement. The anvil begins in the retracted
position, which further complicates and increases the size of the
drive mechanism. Furthermore, the method of activation by
compressing the air to full energy and then releasing off the tip
of the gear while under full load causes severe mechanism wear.
A third technique uses flywheels as energy storage means. The
flywheels are used to launch a hammering anvil impacting the nail.
The examples of this design are U.S. Pat. No. 4,042,036 to Smith et
al., U.S. Pat. No. 5,511,715 to Crutcher et al. and U.S. Pat. No.
5,320,270 to Crutcher. The drawback of this technique is the
problem of coupling the flywheel to the driving anvil. This
technique includes the use of a friction clutching mechanism that
is complicated, heavy and subject to wear. Further limitation of
this approach is the difficulty in controlling the energy in the
fastener driving system, as the mechanism requires enough energy to
drive the fastener, but retains significant energy in the flywheel
after the drive is complete, again increasing the technique
complexity and size.
Accordingly, a need exists to provide an electric motor driven
device for driving fasteners that is unencumbered by fuel cells or
air hoses. What is also needed is a device providing a low
reactionary feel and capable of driving full size fasteners, and
that is simple in configuration, cost-effective and robust in
operation. Further, what is needed is a device that is not
fatiguing, is noiseless, portable, and non-hazardous to a user.
SUMMARY OF THE INVENTION
In view of the foregoing disadvantages inherent in the prior art,
the general purpose of the present invention is to provide a
fastener driving apparatus for driving fasteners into a substrate
to include all the advantages of the prior art, and to overcome the
drawbacks inherent therein.
In one aspect, the present invention provides a fastener driving
apparatus incorporating a slider crank arrangement. The fastener
driving apparatus comprises a power source; a motor electrically
connected to the power source; a first cylinder; a slider crank
arrangement driven by the motor; a second cylinder; and a valve
arrangement operationally disposed between the first cylinder and
the second cylinder. The first cylinder comprises a first piston
reciprocally movable within the first cylinder. The first piston
defines a gas chamber within the first cylinder and the gas chamber
is capable of accommodating gas therein. The slider crank
arrangement operationally coupled to the first piston and
configured to cause the first piston to reciprocally move within
the first cylinder.
The second cylinder comprises a cylinder guide, a second piston
disposed within the cylinder guide. The second piston has a front
face and a rear face, and an anvil coupled to the rear face of the
second piston. The second piston is capable of linearly moving
within the second cylinder thereby enabling the anvil to move in a
driving direction. The valve arrangement defines a gas passageway
for communicating the gas from the first cylinder to the second
cylinder. The gas received within the gas chamber is compressed by
the first piston in a single stroke of the slider crank arrangement
in a manner such that the compressed gas is communicated into the
second cylinder through the gas passageway of the valve
arrangement. This causes the compressed gas to expand in the second
cylinder, thereby causing the second piston to move linearly and
enabling the anvil to drive a fastener into a substrate in the
driving direction in the single stroke of the slider crank
arrangement.
In another aspect, the present invention provides a fastener
driving apparatus incorporating a rack and pinion arrangement. The
fastener driving apparatus comprises a power source; a motor
electrically connected to the power source; a first cylinder; a
rack and pinion arrangement driven by the motor, a second cylinder;
and a valve arrangement operationally disposed between the first
cylinder and the second cylinder. The first cylinder comprises a
first piston reciprocally movable within the first cylinder. The
first piston defines a gas chamber within the first cylinder and
the gas chamber is capable of accommodating gas therein. The rack
and pinion arrangement is driven by the motor, the rack and pinion
arrangement operationally coupled to the first piston and
configured to cause the first piston to reciprocally move within
the first cylinder.
The second cylinder comprises a cylinder guide, a second piston
disposed within the cylinder guide. The second piston has a front
face and a rear face, and an anvil coupled to the rear face of the
second piston. The second piston is capable of linearly moving
within the second cylinder thereby enabling the anvil to move in a
driving direction. The valve arrangement defines a gas passageway
for communicating the gas from the first cylinder to the second
cylinder. The gas received within the gas chamber is compressed by
the first piston in a single stroke of the rack and pinion
arrangement in a manner, such that, the compressed gas is
communicated into the second cylinder through the gas passageway of
the valve arrangement. This causes the compressed gas to expand in
the second cylinder, thereby causing the second piston to move
linearly and enabling the anvil to drive a fastener into a
substrate in the driving direction in the single stroke of the rack
and pinion arrangement.
In yet another aspect, the present invention provides a valve
arrangement for an electric motor driven fastener driving apparatus
for communicating a gas from a first cylinder to a second cylinder
of the fastener driving apparatus. The valve arrangement comprises
a valve body having a central groove; a valve spool disposed within
the central groove; at least one valve retainer configured to
retain the valve spool in an initial closed position; a valve
return spring disposed within the central groove and towards a rear
end portion of the central groove; and a gas passageway configured
from the central groove and continues to the second cylinder. The
gas passageway configures a duct for communicating the gas from the
gas chamber of the first cylinder to the second cylinder.
The valve spool comprises a front face portion, a rear face
portion, a primary body portion, a secondary body portion gradually
extending from the primary body portion in a manner, such that, the
secondary body portion has a diameter less than a diameter of the
primary body portion thereby configuring a chamfered portion there
between, and a valve spool stem extending outwardly from the front
face portion. The valve arrangement is disposed between the first
cylinder and the second cylinder. The gas is compressed by a first
piston within the first cylinder to a compression ratio of
approximately 8:1. Such a compression causes the valve spool to
snap open to an open position against a pressure applied by the
valve retainer and the valve return spring in less than or equal to
about 20 milliseconds in a manner such that the compressed gas from
the first cylinder is communicated through the gas passageway to
the second cylinder. Upon communicating the compressed gas to the
second cylinder, a restoration pressure applied by the valve return
spring to exceed the pressure of the compressed gas in the first
cylinder and enable the valve return spring to restore the valve
spool to the initial closed position.
In yet another aspect, the present invention provides a fastener
driving apparatus capable of driving larger fasteners. The fastener
driving apparatus comprises a power source; a motor electrically
connected to the power source; a first cylinder; a slider crank
arrangement driven by the motor; a second cylinder; and a valve
arrangement operationally disposed between the first cylinder and
the second cylinder. The first cylinder comprises a first piston
reciprocally movable within the first cylinder. The first piston
defines a gas chamber within the first cylinder, the gas chamber
has a separator that divides the gas chamber into a primary gas
chamber and a secondary gas chamber. The primary gas chamber and
the secondary gas chamber are capable of accommodating gas therein.
The slider crank mechanism operationally coupled to the first
piston and configured to cause the first piston to reciprocally
move within the first cylinder.
The second cylinder comprises a cylinder guide, a second piston
disposed within the cylinder guide, the second piston having a
front face and a rear face, and an anvil coupled to the rear face
of the second piston. The second piston is capable of linearly
moving within the second cylinder thereby enabling the anvil to
move in a driving direction. The valve arrangement defines a gas
passageway for communicating the gas from the first cylinder to the
second cylinder. The gas received within the primary gas chamber is
compressed by the first piston in multiple strokes of the slider
crank arrangement in a manner such that the compressed gas is
communicated into the secondary gas chamber in less than or equal
to about 250 milliseconds and with a compression exponent greater
than or equal to about 1.05. For every n revolutions of the slider
crank arrangement, the valve arrangement is caused to open once in
less than or equal to about 250 milliseconds, thereby causing the
compressed gas in the secondary gas chamber to be communicated to
the second cylinder through the gas passageway. This causes the
compressed gas to expand in the second cylinder thereby causing the
second piston to move linearly and enabling the anvil to drive a
fastener into a substrate in the driving direction.
In yet another embodiment, the present invention provides a more
compact and ergonomic fastener driving apparatus incorporating a
crankshaft and connecting rod arrangement. The fastener driving
apparatus comprises a power source; a motor electrically connected
to the power source; a first cylinder; a crankshaft and connecting
rod arrangement driven by the motor, a second cylinder; and a valve
arrangement. The first cylinder is aligned in parallel to the
second cylinder with the valve arrangement operationally disposed
over the first cylinder and the second cylinder. The first cylinder
comprises a first piston reciprocally movable within the first
cylinder. The first piston defines a gas chamber within the first
cylinder and the gas chamber is capable of accommodating gas
therein. The crankshaft and connecting rod arrangement is driven by
the motor, the crankshaft and connecting rod arrangement
operationally coupled to the first piston and configured to cause
the first piston to reciprocally move within the first
cylinder.
The second cylinder comprises a cylinder guide, a second piston
disposed within the cylinder guide. The second piston has a front
face and a rear face, and an anvil coupled to the rear face of the
second piston. The second piston is capable of linearly moving
within the second cylinder thereby enabling the anvil to move in a
driving direction. The valve arrangement defines a gas passageway
for communicating the gas from the first cylinder to the second
cylinder. The gas received within the gas chamber is compressed by
the first piston in a single stroke of the crankshaft and
connecting rod arrangement in a manner such that the compressed gas
is communicated into the second cylinder through the gas passageway
of the valve arrangement. This causes the compressed gas to expand
in the second cylinder, thereby causing the second piston to move
linearly and enabling the anvil to drive a fastener into a
substrate in the driving direction in the single stroke of the
crankshaft and connecting rod arrangement.
These together with other aspects of the present invention, along
with the various features of novelty that characterize the
invention, are pointed out with particularity in the claims annexed
hereto and form a part of this disclosure. For a better
understanding of the invention, its operating advantages, and the
specific objects attained by its uses, reference should be made to
the accompanying drawings and descriptive matter in which there are
illustrated exemplary embodiments of the present invention.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
The advantages and features of the present invention will become
better understood with reference to the following detailed
description and claims taken in conjunction with the accompanying
drawings, wherein like elements are identified with like symbols,
and in which:
FIG. 1 is a longitudinal cross-sectional view of the fastener
driving apparatus 1000, incorporating a slider crank arrangement
100 illustrating a first piston 220 of a first cylinder 200 moving
from a first position towards a second position and intake of gas
into the first cylinder 200, according to an exemplary embodiment
of the present invention;
FIG. 2 is a longitudinal cross-sectional view of the fastener
driving apparatus 1000, illustrating the first piston 220 reaching
the second position, according to an exemplary embodiment of the
present invention;
FIG. 3 is a longitudinal cross-sectional view of the fastener
driving apparatus 1000, illustrating the first piston 220 moving
from the second position towards the first position, according to
an exemplary embodiment of the present invention;
FIG. 4 is longitudinal cross-sectional view of the fastener driving
apparatus 1000, illustrating a partially opened valve arrangement
300, according to an exemplary embodiment of the present
invention;
FIG. 5 is longitudinal cross-sectional view of the fastener driving
apparatus 1000, illustrating a completely opened valve arrangement
300, according to an exemplary embodiment of the present
invention;
FIG. 6 is a top view of the valve arrangement 300, illustrating an
initial closed position of the valve arrangement 300, according to
an exemplary embodiment of the present invention;
FIG. 7 is a partial top view of the valve arrangement 300,
illustrating a tipping point 370 of the valve arrangement 300,
according to an exemplary embodiment of the present invention;
FIG. 8 is a top view of the valve arrangement 300, illustrating an
open position of the valve arrangement 300, according to an
exemplary embodiment of the present invention;
FIG. 9 is a side view of the valve arrangement 300 coupled to first
cylinder 200, illustrating a gas passageway 360, according to an
exemplary embodiment of the present invention;
FIG. 10 is a longitudinal cross-sectional view of a fastener
driving apparatus 2000 incorporating a rack and pinion arrangement
2100 in a first position, according to another exemplary embodiment
of the present invention;
FIG. 11 is a longitudinal cross-sectional view of the fastener
driving apparatus 2000 incorporating the rack and pinion
arrangement 2100 in an intermediate position, according to another
exemplary embodiment of the present invention;
FIG. 12 is a longitudinal cross-sectional view of the fastener
driving apparatus 2000, incorporating the rack and pinion
arrangement 2100 and illustrating a partially opened valve
arrangement 300, according to another exemplary embodiment of the
present invention;
FIG. 13 is a longitudinal cross-sectional view of the fastener
driving apparatus 2000, incorporating the rack and pinion
arrangement 2100 in a second position and illustrating a completely
opened valve arrangement 300, according to another exemplary
embodiment of the present invention;
FIG. 14 is longitudinal cross-sectional view of the fastener
driving apparatus 2000, illustrating the valve arrangement 300 in a
closed position, the rack and pinion arrangement 2100 moving from
the second position towards the first position and intake of gas
into a first cylinder 200, according to another exemplary
embodiment of the present invention;
FIG. 15 is a longitudinal cross-sectional view of a fastener
driving apparatus 3000 incorporating a crankshaft and connecting
rod arrangement 3100 and illustrating the crankshaft and connecting
rod arrangement 3100 moving from a first position towards a second
position and intake of gas into a first cylinder 200, according to
yet another exemplary embodiment of the present invention;
FIGS. 15A to 19A illustrate perspective views of the crankshaft and
connecting rod arrangement 3100, according to yet another exemplary
embodiment of the present invention;
FIG. 16 is a longitudinal cross-sectional view of a fastener
driving apparatus 3000 illustrating a crankshaft and connecting rod
arrangement 3100 in a second position, according to yet another
exemplary embodiment of the present invention;
FIG. 17 is a longitudinal cross-sectional view of a fastener
driving apparatus 3000 illustrating a crankshaft and connecting rod
arrangement 3100 in an intermediate position, according to yet
another exemplary embodiment of the present invention;
FIG. 18 is a longitudinal cross-sectional view of a fastener
driving apparatus 3000 illustrating a crankshaft and connecting rod
arrangement 3100 moving towards the first position and a valve
arrangement 300 in a partially opened position, according to yet
another exemplary embodiment of the present invention;
FIG. 19 is a longitudinal cross-sectional view of a fastener
driving apparatus 3000 illustrating a crankshaft and connecting rod
arrangement 3100 at the first position and the valve arrangement
300 in a completely opened position, according to yet another
exemplary embodiment of the present invention;
FIGS. 20-23 are longitudinal cross-sectional views of a fastener
driving apparatus 4000 illustrating a first stroke of the fastener
driving apparatus 4000 incorporating a slider crank arrangement
4100 and a cam arrangement 4200, according to yet another exemplary
embodiment of the present invention;
FIGS. 24-28 are longitudinal cross-sectional views of the fastener
driving apparatus 4000 illustrating a second stroke of the fastener
driving apparatus 4000 incorporating the slider crank arrangement
4100 and the cam arrangement 4200, according to yet another
exemplary embodiment of the present invention;
FIG. 29 is a top view of a valve arrangement 4300, illustrating an
initial closed position of the valve arrangement 4300, according to
yet another exemplary embodiment of the present invention;
FIG. 30 is a partial top view of the valve arrangement 4300,
illustrating a tipping point 370 of the valve arrangement 4300,
according to yet another exemplary embodiment of the present
invention;
FIG. 31 is a top view of the valve arrangement 4300, illustrating
an open position of the valve arrangement 4300, according to yet
another exemplary embodiment of the present invention; and
FIG. 32 is a side view of the valve arrangement 4300 coupled to a
secondary gas chamber 4260, illustrating a gas passageway 360,
according to yet another exemplary embodiment of the present
invention.
Like reference numerals refer to like parts throughout the
description of several views of the drawings.
DETAILED DESCRIPTION OF THE INVENTION
The exemplary embodiments described herein detail for illustrative
purposes are subject to many variations in structure and design. It
should be emphasized, however, that the present invention is not
limited to a particular fastener driving apparatus, as shown and
described. It is understood that various omissions and
substitutions of equivalents are contemplated as circumstances may
suggest or render expedient, but these are intended to cover the
application or implementation without departing from the spirit or
scope of the claims of the present invention. The terms "first,"
"second," and the like, herein do not denote any order, quantity,
or importance, but rather are used to distinguish one element from
another, and the terms "a" and "an" herein do not denote a
limitation of quantity, but rather denote the presence of at least
one of the referenced item.
The present invention provides a fastener driving apparatus for
driving fasteners into a substrate. As used herein, "fasteners"
refer to objects, such as nails, staples, and the like. The
fastener driving apparatus is a combination of a motor driven
linear motion converter; a compression cylinder; an expansion
cylinder and a valve arrangement. As used herein, the linear motion
converter converts a rotational motion of a motor to a linear
motion of a piston. The linear motion converter is capable of
compressing a gas inside the compression cylinder. The compressed
gas is thereafter communicated to the expansion cylinder through
the valve arrangement. The compressed gas is allowed to expand
within the expansion cylinder, enabling an expansion piston of the
expansion cylinder to exert pressure on a fastener, thereby driving
the fastener into a substrate. The disclosed apparatus is
ergonomically designed to meet the requirements of a portable hand
tool that provides comfort to a user, while at the same time
meeting the safety standards and performance efficiency
requirements. The apparatus has reduced configurational
complexities and avoids usage of fuel cells, reduces wear and tear
of components of the apparatus, is robust in operation, may be mass
manufactured in a-cost effective manner, and provides a portable,
noiseless, non-fatiguing, non-hazardous hand held tool for
users.
Referring to FIGS. 1-5, in one embodiment, a longitudinal
cross-sectional view of a fastener driving apparatus 1000
incorporating a slider crank arrangement is shown. The fastener
driving apparatus 1000 comprises a start switch 10; a motor 20; a
power source 30; a control circuit 40; a gear reduction mechanism
50; a linear motion converter (in this embodiment, a slider crank
arrangement 100); a first cylinder 200; a valve arrangement 300;
and a second cylinder 400. The fastener driving apparatus 1000 is
capable of driving a fastener 500 into a substrate 600 (See FIG. 5)
by utilizing power of a gas compressed within the first cylinder
200. The compressed gas is communicated to the second cylinder 400
through the valve arrangement 300 and enables the compressed gas to
expand in the second cylinder 400, thereby applying pressure to the
fastener 500 for driving the fastener 500 into the substrate
600.
When a user presses the start switch 10 or any other similar
trigger, power from the power source 30 is directed to the motor 20
through the control circuit 40 in a manner such that the motor 20
generates a rotational motion. The rotational motion generated by
the motor 20 is communicated to the slider crank arrangement 100
using the gear reduction mechanism 50. The gear reduction mechanism
50 comprises a plurality of gears that transfers the rotational
motion of a shaft (not shown) of the motor 20 to the slider crank
arrangement 100. The slider crank arrangement 100 is coupled to the
gear reduction mechanism 50. The coupling may be by way of a
plurality of arrangements such as, but not limited to, a worm gear,
a planetary gear, a spur gear, a helical gear or a timing belt. For
the purposes of illustration, a worm gear 110 is shown in the
figures. Accordingly, the slider crank arrangement 100 is coupled
to the worm gear 110 in a manner such that the rotational motion of
the shaft of the motor is transferred to the rotational motion of
the worm gear 110. The worm gear 110 is coupled to a crank wheel
120. A first end 132 of a crank link 130 is coupled to the crank
wheel 120. The rotational motion of the worm gear 110 imparts a
rotational motion to the crank wheel 120 and in turn to the crank
link 130.
The first cylinder 200 comprises a cylinder guide 210 and a first
piston 220 disposed therein. The first piston 220 is coupled at a
second end 134 of the crank link 130 using a connector 136 in a
manner such that the rotational motion of the worm gear 110 and the
crank wheel 120 is converted to linear reciprocal motion of the
first piston 220 within the first cylinder 200 using the crank link
130. The first cylinder 200 further comprises a first cylinder end
cap 240 towards a first end of the first cylinder 200. The first
piston 220 defines a gas chamber 250 within the first cylinder 200
and between the first cylinder end cap 240 and the first piston
220. The gas chamber 250 is capable of accommodating gas therein.
In one embodiment, the first cylinder 200 further comprises a check
valve 230 disposed on the first piston 220. However, the check
valve 230 may be positioned at a variety of locations in the first
cylinder 200. The check valve 230 operates in a manner such that
when the check valve 230 is in an open position, the check valve
230 enables the entry of gas into the gas chamber 250.
Alternatively, when in a closed position, the check valve 230
prevents any exit of gas from the gas chamber 250.
The second cylinder 400 comprises a cylinder guide 410 and a second
piston 420 disposed there within. The second piston 420 has a front
face 422 and a rear face 424. The rear face 424 of the second
piston 420 is coupled to an anvil 430 using a connector 440. The
anvil 430 extends along a longitudinal axis of the second cylinder
400 into a fastener guide 530. The anvil 430 is capable of linearly
moving within the second cylinder 400 and the fastener guide 530.
The fastener guide 530 is configured to receive a fastener 500 from
a fastener feeder 550 and the linearly moving anvil 430 is capable
of applying pressure to the fastener 500 in the fastener guide 530.
Additionally, the linear movement of the anvil 430 through the
fastener guide 530 enables in jamb clearing. Such a jamb clearing
removes the fastener fragments or other debris inside the fastener
guide 530 with the linear movement of the anvil 430 through the
fastener guide 530 and thereby avoids the need of any manual
operation for cleaning the fastener guide 530.
The second cylinder 400 further comprises an anvil retracting
mechanism 450 and an anvil drive bumper 460. The anvil drive bumper
460 is disposed at an end of the second cylinder 400 away from an
end having the valve arrangement 300. In one embodiment, the anvil
retracting mechanism 450 is a return spring and is coupled to the
rear face 424 of the second piston 420 at one end and to the anvil
drive bumper 460 at another end. Alternatively, the anvil
retracting mechanism 450 may be an extension spring or rubber
bungee attached to the front face 422 and to the valve arrangement
300. In a situation when the second cylinder 400 has not received
the compressed gas from the first cylinder 200, the second piston
420 is positioned towards the valve arrangement 300 and the anvil
retracting mechanism 450 is in a relaxed position i.e. the anvil
retracting mechanism 450 is not compressed. Such a position is also
referred to as the load-free position. The anvil retracting
mechanism 450 is configured to retract the second piston 420 back
to an original position towards the valve arrangement 300.
The first cylinder end cap 240 is coupled to the valve arrangement
300. Referring to FIGS. 6-9, the valve arrangement 300 is
illustrated in detail. The first cylinder end cap 240 has a central
hollow portion 242. The valve arrangement 300 comprises a valve
body 310 having a central groove 312 extending along a longitudinal
axis X-X of the valve body 310. The central groove 312 conforms to
the central hollow portion 242 of the first cylinder end cap 240 at
the front end portion, while the rear end portion of the central
groove 312 is closed. A valve spool 320 is seated up against the
valve body 310 within the central groove 312 along the longitudinal
axis X-X and is capable of reciprocating linearly within the
central groove 312. In one embodiment, the valve spool 320 has a
cylindrical body having a stepped structure configured by a primary
body portion 322 and a concentric secondary body portion 324.
The primary body portion 322 has a diameter greater than a diameter
of the secondary body portion 324. The secondary body portion 324
gradually extends from the primary body portion 322 in a manner
such that the graduation of the primary body portion 322 into the
secondary body portion 324 configures a chamfered portion 326 (see
FIG. 8). The valve spool 320 reciprocates within the central grove
312 of the valve body 310 along the longitudinal axis X-X. The
valve spool 320 further has a front face portion 328, a rear face
portion 330 and a valve spool stem 332 extending outwardly from the
front face portion 328 along a longitudinal axis of the valve spool
320. In an initial state, the front face portion 328 is positioned
in the central hollow portion 242 of the first cylinder end cap 240
in a manner such that the front face portion 328 closes the central
hollow portion 242, while the valve spool stem 332 extends into the
gas chamber 250 of the first cylinder 200.
The valve arrangement 300 further comprises a pair of valve
retainers 340 positioned in an opposed relationship laterally along
the central groove 312 of the valve body 310. In one embodiment,
each valve retainer 340 is in the form of a cup 342 and retention
ball 344. In the initial state, when the valve spool 320 is closing
the central hollow portion 242 of the first cylinder end cap 240,
the valve spool 320 is retained in such a position by the valve
retainers 340. The valve retainers 340 are positioned in a manner
such that the retention balls 344 are disposed at the chamfered
portion 326 of the valve spool 320, thereby applying pressure on
the valve spool 320 and preventing the valve spool 320 to deviate
from the position closing the central hollow portion 242 of the
first cylinder end cap 240. Additionally, the valve arrangement 300
comprises a valve return spring 350 disposed within the central
groove 312 and towards the rear end portion of the central groove
312. The rear face portion 330 of the valve spool 320 is disposed
on the valve return spring 350. The valve arrangement 300 further
comprises a gas passageway 360 configured from the central groove
312 of the valve arrangement 300 and connected to the second
cylinder 400. In the initial state, when the front face portion 328
of the valve spool 320 is disposed on the central hollow portion
242, the primary body portion 322 substantially closes the gas
passageway 360. The gas passageway 360 is configured to define a
duct for communicating the gas from the gas chamber 250 of the
first cylinder 200 to the second cylinder 400.
More specifically, FIG. 1 illustrates a longitudinal
cross-sectional view of the fastener driving device 1000, showing
an intake of gas into the gas chamber 250 of the first cylinder
200. Preferably, the gas used is the atmospheric air at atmospheric
pressure thereby avoiding the usage of any pre-compressor for
pressurizing the intake air. The cycle begins when the first piston
220 is at a first position close to a top dead center towards the
first cylinder end cap 240 and the crank link 130 is substantially
horizontal with respect to the first cylinder. With the start
switch 10 pressed ON; the motor 20 is powered by the power source
30 using the control circuit 40. The control circuit 40 may be any
apparatus for connecting power to the motor 20 for the purpose of
initiating the operation of the fastener driving device 1000 and
then removing the power to the motor 20 after the operation of the
fastener driving device 1000 has substantially completed. The crank
wheel 120 starts rotating (either clockwise or counterclockwise),
causing the first piston 220 to move linearly away from the first
cylinder end cap 240 within the cylinder guide 210. In this
situation, the check valve 230 opens, causing atmospheric air to
enter the gas chamber 250. The intake of atmospheric air through
the check valve 230 continues until the time the crank wheel 120
has completed enough rotation such that the crank link 130 is once
again horizontal. For an 18 gage nail, the volume of the gas in the
gas chamber 250 ranges from 6 to 9 cubic inches at standard
temperature and pressure conditions and, more preferably, 8 cubic
inches. At this stage, the first piston 220 has reached a second
position (See FIG. 2).
With the continued rotation of the crank wheel 120, the crank link
130 continues its movement corresponding to the rotation of the
wheel 120 another 180 degrees as shown in FIG. 3. The first piston
220 starts moving towards the first cylinder end cap 240 as the
cycle continues. During this cycle, the check valve 230 is in the
closed position, preventing any exit of air from the gas chamber
250. The first piston 220 continuously compresses the air in the
gas chamber 250 while moving towards the first cylinder end cap
240. In this stage the valve spool 320 is also disposed in the
central hollow portion 242 of the first cylinder end cap 240 in a
manner, such that, the valve spool 320 closes the central hollow
portion 242 and the gas passageway 360 is also closed. In such a
position the valve arrangement 300 is more specifically illustrated
in FIG. 6, wherein the valve retainers 340 and the retention balls
344 are disposed at the chamfered portion 326 of the valve spool
320. Such positioning of the retention balls 344 applies pressure
on the valve spool 320 and prevents the valve spool 320 to deviate
from the position closing the central hollow portion 242 of the
first cylinder end cap 240. FIG. 9 illustrates a longitudinal side
view of the valve arrangement 300 in conjunction with the first
cylinder 200, showing the position of the valve spool stem 332
disposed inside the gas chamber 250 when the valve spool 320 is
closing the central hollow portion 242 of the first cylinder end
cap 240.
Referring to FIG. 3, an intermediate position of the first piston
220 between the second position and the first position of the first
piston 220 in the first cylinder 200 is shown. The continued
rotation of the crank wheel 120 causes the first piston 220 to
continue proceeding towards the first cylinder end cap 240, thereby
further compressing the gas in the gas chamber 250.
With a further continued rotation of the crank wheel 120, the first
piston 220 continues proceeding towards the first cylinder end cap
240, thereby further compressing the gas in the gas chamber 250.
The valve arrangement 300 opens either when the gas pressure inside
the gas chamber 250 exceeds the maintaining pressure of the valve
spool 320 of the valve arrangement 300 or when the first piston 220
strikes the valve spool stem 332 of the valve spool 320. The valve
arrangement 300 remains open with the gas pressure from the gas
chamber 250 until the force of the gas pressure drops below the
restoring force of the valve return spring 350. Accordingly, the
pressure inside the gas chamber 250 increases to an extent that the
pressure of the gas in the gas chamber 250 exceeds the pressure
applied by the valve retainers 340 and the valve return spring 350
on the valve spool 320. In such a situation, the gas inside the gas
chamber 250 pushes the valve spool 320 to move linearly inside the
central groove 312 of the valve body 310 in a manner such that the
valve spool 320 opens central hollow portion 242. The position of
the valve arrangement in this situation may be more specifically
referred to in FIG. 7, when the valve spool 320 opens the central
hollow portion 242, the retention balls 344 cross a tipping point
370. The tipping point 370, as used herein, refers to a point of
contact between the retention balls 344 and the valve spool 320,
when the valve retainers 340 and the retention balls 344 provide
minimal resistance to the linear movement of the valve spool 320,
thereby resulting in an opening of the gas passageway 360.
The movement of the first piston 220 creates the timing for opening
of the valve spool 320 of the valve arrangement 300. The first
piston 220 pushes the valve spool 320 to open the valve arrangement
300 before the first piston 220 reaches the first position (top
dead center). The advantage of opening of the valve arrangement 300
while the first piston 220 is still advancing is that the pressure
in the gas chamber 250 cannot force the first piston 220 back.
Additionally, if the valve arrangement 300 opens too early, the
pressure offered by the gas chamber 250 would be insufficient
pressure to drive the second piston 420 for driving the fastener
500 into the substrate 600. Furthermore, if the valve arrangement
300 opens too late, first piston 220 starts to return before the
anvil 430 drives the fastener 500 into the substrate 600.
The opening of the valve arrangement 300 on sufficiently
compressing the gas in the gas chamber 250 includes several
parameters that are important for the configurational features of
the valve arrangement 300. The parameters are the pressure drop
through the valve arrangement 300, the opening time of the valve
arrangement 300 and the volume of air contained in gas passageway
360. In a preferred embodiment, the valve arrangement 300 is
referred to as a snap acting valve. More specifically, the opening
time of the valve spool 320, i.e. the time from being closed until
the time the valve is at least 70 percent open, should be less than
20 milliseconds (0.020 seconds.) The valve spool 320 needs to open
fully and quickly such that the energy of expansion is not lost to
the spool 320 and the valve retainers 340. If the valve were to
open in 0.100 seconds, for example, the energy of expansion would
be lost to the valve spool 320 and the valve retainers 340, and the
ability to transfer the energy from the compressed gas into the
second cylinder 400 and to the anvil 430 would be greatly
restricted. This would cause a larger reactionary force against the
user and would make difficult the ability of the apparatus to drive
fasteners. The valve arrangement 300 and more specifically, the
valve spool 320 may be mechanically tripped during a single stroke
of the first piston 220 by at least one of an electric motor, the
first piston and a cam.
In one embodiment, the opening force that may drive a standard 18
gage 2'' long fastener, for example a nail, fully into pine
substrate is the force when the gas in the gas chamber 250 is
compressed to approximately 160 psi with a volume of approximately
1.0 cubic inch. The volume of gas contained in gas passageway 360
should be less than 10 percent of the initial uncompressed volume
of gas in the gas chamber 250, when the first piston 220 is in
first position, for fully driving the fastener.
Thus the valves, which open quickly, fully and do not have too high
volume in the gas passageway, enable driving of the fastener fully
into the substrate. Furthermore, a high Cv (flow coefficient of a
valve and relates the pressure drop across the valve to the flow
through the valve) characteristic and snap action features of valve
arrangement 300 with the low volume of gas contained within the gas
passageway 360 result in a significant reduction of the compression
energy and increases the life of the power source, such as a
battery, by 30 percent. The high Cv valve arrangement gives a
larger flow of gas through a valve arrangement at a given pressure
drop than a low Cv valve arrangement. The configurational features
of the valve arrangement 300 in combination with the high Cv
results in very fast opening speed and very efficient conversion of
the energy of the gas from the gas chamber 250 through the valve
arrangement 300 such that the anvil 430 drives the fastener 500
into the substrate 600 in an efficient manner.
After the tipping point 370, the valve retainers 340 only provide a
frictional force to the valve spool 320. This frictional force is
far less than the direct force afforded by the valve retainers 340
on the valve spool 320. In the embodiment shown, once the retention
balls 344 ride up the chamfered portion 326 on the valve spool 320,
the force from the retention balls 344 to maintain the valve spool
320 in its position changes from 45 degrees (or the angle of the
chamfered portion 326) to 90 degrees, which is perpendicular to the
movement of the valve spool 320. This essentially removes the
retention balls 344 and the valve retainers 340 from retaining the
valve spool 320, as the valve retainers 340 acting perpendicular to
the valve spool movement and can no longer restrain the valve spool
320. The only force maintaining the valve spool 320 in the closed
position is the force from the valve return spring 350. This is
substantially less than the compressed gas pressure that is applied
to a face of the valve spool 320, thus the valve spool 320 snaps
open.
The compressed gas in the gas chamber 250 of the first cylinder 200
starts passing into the second cylinder 400 through the gas
passageway 360, as shown using arrows in FIG. 4. The compressed gas
reaching the second cylinder starts expanding thereby applying
pressure on the front face 422 of the second piston 420 which
causes the second piston 420 to move axially towards the anvil
drive bumper 460. The anvil 430 accordingly moves axially into the
fastener guide 530. The anvil retracting mechanism 450 gets
compressed, thereby storing energy into the anvil retracting
mechanism 450.
Referring to FIG. 5, the further continued rotation of the crank
wheel 120 causes the first piston 220 to continue proceeding
towards the first cylinder end cap 240, thereby forcing the
compressed gas in the gas chamber 250 to the second cylinder 400
through the gas passageway 360 which is fully open (see FIG.
8).
In another embodiment of the present invention, the first piston
220 applies pressure on the valve spool stem 332 while proceeding
towards the first cylinder end cap 240, thereby causing the valve
spool 320 to open up the gas passageway 360 in addition to the
compressed gas pressure within the gas chamber 250. The valve spool
stem 332 allows the first piston 220 to hold the valve spool 320
open even when the pressure in the gas chamber 250 drops. This
further improves the efficiency of the valve arrangement 300 since
the valve spool 320 is held open even if the pressure in the gas
chamber 250 drops below the pressure required to hold the valve
spool 320 open against the restoring force of the valve return
spring 350.
Once the valve spool 320 is opened, it is maintained open by the
compressed gas pressure from the gas chamber 250 until a force from
the compressed gas pressure drops below the restoring force of the
valve return spring 350. Finally, with the crank wheel 120
completing the second 180 degrees of rotation, the first piston 220
reaches the first position within the first cylinder 200. This
causes the maximum amount of compressed gas in the gas chamber 250
to be delivered to the second cylinder 400 through the gas
passageway 360. The compressed gas in the second cylinder 400
expands therein and applies pressure on the second piston 420
causing it to move axially further towards the anvil drive bumper
460. The anvil 430 axially moves further into the fastener guide
530 and applies pressure on the fastener 500 disposed from the
fastener feeder 550 into the fastener guide 530. Due to the applied
pressure by the anvil 430, the fastener 500 is driven into the
substrate 600 such that the fastener driving device 1000 completes
a single stroke.
The single stroke compression enables compressing the gas in the
gas chamber 250 such that the compression exponent of the gas
inside the gas chamber 250 is greater then 1.0. The compression
exponent greater than 1.0 yields higher gas pressure for a given
compression ratio and increases the volumetric efficiency of the
configurational aspect of the fastener driving device 1000 by
allowing more energy to be stored in a volume of gas compared to
the compression done via a normal multi-stroke compressor in which
the heat of compression is lost to the environment. In the present
embodiment, the fastener driving apparatus 2000 has an efficient
design such that the single stoke operation is sufficiently short
(in terms of time) to yield a compression exponent of approximately
1.1.
Upon completion of the stroke, i.e. upon the first piston 220
reaching the first position, a maximum amount of compressed gas is
delivered to the second cylinder 400. The pressure inside the gas
chamber 250 falls below the pressure applied by the valve return
spring 350 which thereby applies pressure on the valve spool 320
causing the valve spool 320 to return to the closed position (i.e.
the valve spool 320 is disposed back into the central hollow
portion 242 of the first cylinder end cap 240.) Accordingly, with
each triggering (i.e., powering of the switch 10), one fastener 500
is punched into the substrate 600. The fastener driving apparatus
1000 is ready for the next operation.
The fastener driving apparatus 1000 further comprises a plurality
of sensors (not shown) that aides the control circuit 40 in knowing
where exactly is the first piston 220 at certain points in the
cycle. The sensors may be placed on the first piston 220, any gear
of the gear reduction 50 or on the valve arrangement 300. When the
control circuit 40 picks up one of these sensors, the control
circuit 40 knows the position of the first piston 220 within the
first cylinder 200. In one embodiment, the sensor is placed in the
valve arrangement 300 and a magnet (not shown) is disposed on a
piston head of the first piston 220. This allows the control
circuit 40 to know when the first piston 220 is approaching or
leaving the first position (top dead center). When a cycle is
underway and upon receiving feedback from a sensor, the control
circuit 40 may apply the brake to the motor 20 to stop the
operation of the fastener driving apparatus 1000 in a predetermined
location.
In yet another embodiment, the fastener driving apparatus 1000 may
be coupled with a clutch (not shown). Generally the operation
begins with the motor 20 activating, moving the slider crank
arrangement 100, firing the valve arrangement 300 and then
stopping. If a clutch is used, the motor 20 may be allowed to run
continuously. For example, when a nosepiece (i.e., a fastener guide
530) of the fastener driving apparatus 1000 is positioned against
the substrate 600, the motor 20 may be started. In this way, energy
necessary to drive a fastener into the substrate 600 is in the
motor 20 before being transferred to the slider crank arrangement
100.
When the user pulls the start switch (trigger), this engages the
clutch, which in turn engages the slider crank arrangement 100.
Because the motor is not starting from a "dead stop," energy can be
extracted right away and much more quickly. Motors generally have
the most power in the midrange of their operating range of
revolutions per minute (RPMs). These motors deliver no power at the
start (as they are not rotating yet) and are less efficient at
lower RPMs than at higher RPMs. If the fastener driving apparatus
1000 is engaged in this fashion, the fastener driving apparatus has
a much more responsive feel. For example, by using the fastener
driving apparatus 1000 of the present invention, the time from a
trigger pull to driving an 18 gage 2'' long fastener may be reduced
from about 100 milliseconds to about 50 milliseconds while creating
a much more responsive tool feel to the professional user.
Referring to FIGS. 10-14, in another embodiment, a longitudinal
cross-sectional view of a fastener driving apparatus 2000
incorporating a rack and pinion arrangement 2100 is shown. The
fastener driving apparatus 2000 is similar to the configurational
aspects of the fastener driving apparatus 1000 and comprises a
switch 10; a motor 20; a power source 30; a control circuit 40; a
gear reduction mechanism 50; a linear motion converter, for
example, a rack and pinion arrangement 2100 in this embodiment; a
first cylinder 200; a valve arrangement 300; and a second cylinder
400. The fastener driving apparatus 2000 is capable of driving a
fastener 500 into a substrate 600 by utilizing power of a gas
compressed within the first cylinder 200. The compressed gas is
communicated to the second cylinder 400 through the valve
arrangement 300 and enables the compressed gas to expand in the
second cylinder 400, thereby applying pressure to the fastener 500
for driving the fastener 500 into the substrate 600.
When a user presses the start switch 10, power from the power
source 30 is directed to the motor 20 through the control circuit
40 in a manner such that the motor 20 generates a rotational
motion. The rotational motion generated by the motor 20 is
communicated to the linear motion converter, which is the rack and
pinion arrangement 2100 in this embodiment, using the gear
reduction mechanism 50. The gear reduction mechanism 50 comprises a
plurality of gears as shown in FIGS. 10-14, and transfers the
rotational motion of a shaft (not shown) of the motor 20 to the
rack and pinion arrangement 2100. The rack and pinion arrangement
2100 comprises a pinion 2200 coupled to a worm gear 110, each
disposed upon the same shaft (not shown), that is coupled to one of
the gears of the gear reduction mechanism 50; a rack 2300 coupled
to the first piston 220 about a first end portion (not shown) of
the rack 2300; a first return spring 2400 coupled to the rack 2300
with a return spring connector 2410 about a second end portion (not
shown) of the rack 2300; and a support bearing 2500 positioned
between a cylinder guide 210 of the first cylinder 200 and the rack
2300. The rack 2300 may be coupled to the first piston 220 by a
variety of mechanisms including, but not limited to, press fitting,
screwing, pinning, or the like. In the present embodiment the rack
2300 is coupled to the first piston 220 with a screw 2310. The
first return spring 2400 is responsible for retracting the rack
2300 and first piston 220 toward a first position (bottom dead
center) of the first cylinder 200. The first return spring 2400 is
a constant force spring (similar to a tape measure).
The first return spring 2400 extends when the rack and pinion
arrangement 2100 moves towards a second position (top dead center)
under the gear reduction mechanism 50 drive. The first return
spring 2400 returns the rack 2300 to a first position (bottom dead
center) when the pinion 2200 disengages from the rack 2300. The
support bearing 2500 supports the rack 2300 against the pinion 2200
and keeps the rack 2300 in alignment with the first piston 220
about the first cylinder 200. The rack 2300 has rack teeth 2324
configured on a partial length on one side of the rack 2300. The
pinion 2200 has pinion teeth 2202 configured on a partial length of
a circumference of the pinion 2200. With the application of
pressure by the support bearing 2500, at least one tooth from the
rack teeth 2324 of the rack 2300 mesh with at least one tooth from
the pinion teeth 2202 of the pinion 2200.
The first cylinder 200 further comprises a first cylinder end cap
240 towards an end of the first cylinder 200. The first piston 220
defines a gas chamber 250 within the first cylinder 200 and between
the first cylinder end cap 240 and the first piston 220. The gas
chamber 250 is capable of accommodating gas therein. The first
cylinder 200 further comprises a check valve 230 disposed on the
first piston 220. The check valve 230 is configured to operate in a
manner such that when the check valve 230 is in an open position,
the check valve 230 enables the entry of gas into the gas chamber
250 of the first cylinder 200 and when in a closed position, the
check valve 230 prevents any exit of gas from the gas chamber
250.
The first cylinder end cap 240 is coupled to the valve arrangement
300. Referring to FIGS. 6-9, the valve arrangement 300 is
illustrated in detail. The first cylinder end cap 240 has a central
hollow portion 242. The valve arrangement 300 comprises a valve
body 310 having a central groove 312 extending along a longitudinal
axis X-X of the valve body 310. The central groove 312 conforms to
the central hollow portion 242 of the first cylinder end cap 240 at
the front end portion, while the rear end portion of the central
groove 312 is closed. A valve spool 320 is seated up against the
valve body 310 within the central groove 312 along the longitudinal
axis X-X and is capable of reciprocating linearly within the
central groove 312. In one embodiment, the valve spool 320 has a
cylindrical body having a stepped structure configured by a primary
body portion 322 and a concentric secondary body portion 324.
The primary body portion 322 has a diameter greater than a diameter
of the secondary body portion 324. The primary body portion 322
gradually extends into the secondary body portion 324 in a manner
such that the graduation of the primary body portion 322 into the
secondary body portion 324 configures a chamfered portion 326 (see
FIG. 8). The valve spool 320 reciprocates within the central grove
312 of the valve body 310 along the longitudinal axis X-X. The
valve spool 320 further has a front face portion 328, a rear face
portion 330 and a valve spool stem 332 extending outwardly from the
front face portion 328 along a longitudinal axis of the valve spool
320. In an initial state, the front face portion 328 is positioned
in the central hollow portion 242 of the first cylinder end cap 240
in a manner such that the front face portion 328 closes the central
hollow portion 242, while the valve spool stem 332 extends into the
gas chamber 250 of the first cylinder 200.
The valve arrangement 300 further comprises a pair of valve
retainers 340 positioned in an opposed relationship laterally along
the central groove 312 of the valve body 310. In one embodiment,
each valve retainer 340 is in the form of a cup 342 and retention
ball 344. In the initial state, when the valve spool 320 is closing
the central hollow portion 242 of the first cylinder end cap 240,
the valve spool 320 is retained in such a position by the valve
retainers 340. The valve retainers 340 are positioned in a manner
such that the retention balls 344 are disposed at the chamfered
portion 326 of the valve spool 320, thereby applying pressure on
the valve spool 320 and preventing the valve spool 320 to deviate
from the position closing the central hollow portion 242 of the
first cylinder end cap 240.
Additionally, the valve arrangement 300 comprises a valve return
spring 350 disposed within the central groove 312 and towards the
rear end portion of the central groove 312. The rear face portion
330 of the valve spool 320 is disposed on the valve return spring
350. The valve arrangement 300 further comprises a gas passageway
360 configured from the central groove 312 of the valve arrangement
300 and connected to the second cylinder 400. In the initial state,
when the front face portion 328 of the valve spool 320 is disposed
on the central hollow portion 242, the primary body portion 322
closes the gas passageway 360. The gas passageway 360 is configured
to define a duct for communicating the gas from the gas chamber 250
of the first cylinder 200 to the second cylinder 400.
The second cylinder 400 comprises a cylinder guide 410 and a second
piston 420 disposed there within. The second piston 420 has a front
face 422 and a rear face 424. The rear face 424 of the second
piston 420 is coupled to an anvil 430 using a connector 440. The
anvil 430 extends along a longitudinal axis of the second cylinder
400 into a fastener guide 530. The anvil 430 is capable of linearly
moving through the second cylinder 400 and the fastener guide 530.
The fastener guide 530 is configured to receive a fastener 500 from
a fastener feeder 550 and the linearly moving anvil 430 is capable
of applying pressure to the fastener 500 in the fastener guide 530.
The second cylinder 400 further comprises an anvil retracting
mechanism (return spring) 450 and an anvil drive bumper 460.
Additionally, the linear movement of the anvil 430 through the
fastener guide 530 enables in jamb clearing. Such a jamb clearing
removes the fastener fragments or other debris inside the fastener
guide 530 with the linear movement of the anvil 430 through the
fastener guide 530 and thereby avoids the need of any manual
operation for cleaning the fastener guide 530.
The anvil drive bumper 460 is disposed at an end of the second
cylinder 400 away from an end having the valve arrangement 300. The
anvil retracting mechanism 450 is coupled to the rear face 424 of
the second piston 420 at one end and to the anvil drive bumper 460
at another end. In a situation when the second cylinder 400 has not
received the compressed gas from the first cylinder 200, the second
piston 420 is positioned towards the valve arrangement 300 and the
anvil retracting mechanism 450 is in a relaxed position i.e. the
anvil retracting mechanism 450 is not compressed. Such a position
is also referred to as the load-free position. The anvil retracting
mechanism 450 is configured to retract the second piston 420 back
to an original position towards the valve arrangement 300.
More specifically, FIG. 10 shows a longitudinal cross-sectional
view of the fastener driving apparatus 2000, illustrating the rack
and pinion arrangement 2100 in a first position. The first position
as used herein refers to the position of the first piston 220 at
bottom dead center and the first piston 220 is near to the support
bearing 2500 with the check valve 230 being closed. In the first
position, the gas chamber 250 is occupied with a volume of gas
proportional to the amount of work to be done by the first piston
220 within the first cylinder 200, for example, the amount of work
required for driving an 18 gage 2'' long fastener. In one
embodiment, the volume of the gas in the gas chamber 250 ranges
from 6 to 9 in.sup.3 at standard temperature and pressure
conditions and, more preferably, 7 in.sup.3. Preferably, the gas
used is the atmospheric air at atmospheric pressure which thereby
simplifies the design of the fastener driving apparatus 2000, as
using air greater than atmospheric pressure might otherwise require
another pre-compressor to increase the pressure of the air inside
the gas chamber 250.
In the first position of the rack and pinion arrangement 2100, when
the start switch 10 is switched ON, power is directed from the
power source 30 to the motor 20 through the control circuit 40. The
control circuit 40 may be any apparatus for connecting power to the
motor 20 for the purpose of initiating the operation of the
fastener driving apparatus 2000 and then removing the power to the
motor 20 after the operation of the fastener driving apparatus 2000
has substantially completed. The first return spring 2400 is in a
relaxed position, when the first piston 220 and the rack 2300 are
at the first position and are about to move from the first position
of the first cylinder 200 towards a second position. The second
position as used herein refers to the position of the first piston
220 at top dead center towards the first cylinder end cap 240 of
the first cylinder 200. In one embodiment, the first return spring
2400 is a constant force spring, similar to a spring used in tape
measuring devices.
Referring now to FIG. 11, illustrated is a longitudinal
cross-sectional view of the fastener driving apparatus 2000,
incorporating the rack and pinion arrangement 2100 in an
intermediate position of the first piston 220 between the first
position and the second position. On receiving power from the power
source 30, the motor 20 directs the shaft (not shown) to rotate,
transferring energy through the gear reduction 50 and worm gear 110
to the rack and pinion arrangement 2100 of the fastener driving
apparatus 2000. More specifically, the worm gear 110 (coupled to
the pinion 2200) rotates the pinion 2200 such that the teeth of the
pinion 2200 mesh with the teeth in the rack 2300. With the
counterclockwise rotation of the pinion 2200 (using the rotation of
the motor 20 and the gear reduction mechanism 50) the rack 2300
that is in mesh with the pinion 2200 begins to move linearly
causing the first piston 220 to move linearly within the first
cylinder 200 towards the second position. At the intermediate
position the air inside the gas chamber 250 of the first cylinder
200 is compressed with a linear forward motion of the first piston
220 and rack 2300. The linear forward motion of the first piston
220 and rack 2300 is the movement of the first piston 220 and rack
2300 from the first position of the first piston 220 towards the
second position of the first piston 220.
The rack 2300 further has a toothless portion 2320 such that one or
more teeth substantially removed behind the initial engagement
teeth 2322 of the rack 2300. The toothless portion 2320 is
responsible for improving the alignment/engagement tolerance for
the engagement between the rack 2300 and the pinion 2200 when the
pinion teeth 2202 of the pinion 2200 start meshing with the rack
teeth 2324 of the rack 2300. The toothless portion 2320 improves
the wear characteristics for the pinion teeth 2202 of the pinion
2200 and the rack teeth 2324 of the rack 2300. This configuration
increases the engagement tolerance of the pinion 2200 to the rack
2300 by more than 50 percent, thereby greatly reducing the
likelihood that the pinion teeth 2202 of the pinion 2200 and the
rack teeth 2324 of the rack 2300 mesh in an interfering
fashion.
More particularly, when an initial engagement tooth 2222 of the
pinion 2200 comes around to engage the initial engagement teeth
2322 of the rack 2300 and there is misalignment between the
position of the initial engagement teeth 2322 of the rack 2300 with
respect to the initial engagement tooth 2222 of the pinion 2200,
there may be a possibility that the initial engagement tooth 2222
may hit the rack teeth 2324 of the rack 2300 instead of hitting the
initial engagement teeth 2322 of the rack 2300 which results in
improper engaging and meshing. Thus, the toothless portion 2320 is
responsible for more tolerance when the pinion teeth 2202 mesh with
the rack teeth 2324.
By limiting the teeth at a back end of the rack 2300, the rack 2300
cannot be driven forward enough to advance the first piston 220
into the first cylinder end cap 240. If there were enough teeth on
the rack 2300, and the rack and pinion arrangement 2100 engaged in
the wrong spot for example, then the first piston 220 could be
driven through impact of the first cylinder end cap 240 and cause
potential damage to the fastener driving apparatus 2000.
Accordingly, even if there were more teeth on the pinion 2200, it
may not force the rack 2300 and the first piston 220 forward.
Therefore, even if the pinion 2200 does not engage properly, the
worst it may do is to move against the last tooth of the rack 2300,
but it may not advance the rack 2300 and the first piston 220 to
impact the face of the valve arrangement 300.
Further, in the intermediate position of the first piston 220, the
movement of the rack 2300 along with the first piston 220 towards
the valve arrangement 300 compresses the gas in the gas chamber 250
and stretches the relaxed first return spring 2400. The gas in the
gas chamber 250 is held between the first piston 220 and the first
cylinder end cap 240 until the valve arrangement 300 opens. During
this cycle, the check valve 230 is in the closed position,
preventing any exit of gas from the gas chamber 250. The first
piston 220 continuously compresses the gas in the gas chamber 250
while moving towards the first cylinder end cap 240. In this stage
the valve spool 320 is also disposed in the central hollow portion
242 of the first cylinder end cap 240 in a manner such that the
valve spool 320 closes the central hollow portion 242 and the gas
passageway 360 is also closed. Such a position of the valve
arrangement 300 is more specifically illustrated, in FIG. 6,
wherein the valve retainers 340 and specifically the retention
balls 344 are disposed at the chamfered portion 326 of the valve
spool 320. Such a positioning of the retention balls 344 applies
pressure on the valve spool 320 and prevents the valve spool 320 to
deviate from the position closing the central hollow portion 242 of
the first cylinder end cap 240.
Referring now to FIG. 12, illustrated is a longitudinal
cross-sectional view of the fastener driving apparatus 2000,
incorporating the rack and pinion arrangement 2100 and depicting a
partially opened valve arrangement 300. The valve arrangement 300
opens either when the gas pressure inside the gas chamber 250
exceeds the maintaining force of the valve spool 320 of the valve
arrangement 300 or when the first piston 220 strikes the valve
spool stem 332 of the valve spool 320. The valve arrangement 300
remains open with the gas pressure from the gas chamber 250 until
the force of the gas pressure drops below the restoring force of
the valve return spring 350 and the valve spool stem 332 no longer
is in contact with the first piston.
In the above mentioned condition, when the valve arrangement 300 is
partially open, the further movement of the pinion 2200, the rack
2300 and the first piston 220 move linearly forward further towards
the second position. Such a movement of the rack 2300 along with
the first piston 220 towards the valve arrangement 300 (i.e. the
second position) compresses the air inside the gas chamber 250.
Accordingly, the pressure inside the gas chamber 250 increases to
an extent that the pressure of the gas in the gas chamber 250
exceeds the pressure applied by the valve retainers 340 and the
valve return spring 350 on the valve spool 320. In such a
situation, the gas inside the gas chamber 250 pushes the valve
spool 320 to move linearly inside the central groove 312 of the
valve body 310 such that, the valve spool 320 opens central hollow
portion 242. The position of the valve arrangement in this
situation may be more specifically referred to in FIG. 7, when the
valve spool 320 opens the central hollow portion 242, and the
retention balls 344 cross a tipping point 370. The tipping point
370, as used herein, refers to a point of contact between the
retention balls 344 and the valve spool 320, when the valve
retainers 340 and the retention balls 344 provide minimal
resistance to the linear movement of the valve spool 320, thereby
resulting in an opening of the gas passageway 360.
At the tipping point 370, the retention balls 344 provide minimal
resistance to the linear movement of the valve spool 320, thereby
resulting in an opening of the gas passageway 360. This enables the
compressed gas within the gas chamber 250 to be released into the
second cylinder 400 through the valve arrangement 300 and, more
specifically, through the gas passageway 360. In another embodiment
of the present invention, the first piston 220 applies pressure on
the valve spool stem 332 while proceeding towards the first
cylinder end cap 240, thereby causing the valve spool 320 to open
up the gas passageway 360 in addition to the compressed gas
pressure within the gas chamber 250. The valve spool stem 332
allows the first piston 220 to hold the valve spool 320 open even
when the pressure in the gas chamber 250 drops. Thus, the valve
spool stem 332 improves the efficiency of the valve arrangement 300
since the valve spool 320 is held open even if the pressure in the
gas chamber 250 drops below the pressure required to hold the valve
spool 320 open against the restoring force of the valve return
spring 350.
A further advantage of the valve spool stem 332 is that the valve
spool stem 332 avoids allowing the valve spool 320 to remain in a
closed position. Suppose the valve spool 320 remained closed during
a cycle and the pinion 2200 has released the rack 2300, the rack
2300 and first piston 220 would be thrown violently towards support
bearing 2500, since the pressure of the gas inside the gas chamber
250 would have increased and the first return spring 2400 would
pull the rack 2300 and the first piston 220 towards the support
bearing 2500 and thereby causing a potential damage to the fastener
driving apparatus 2000.
The compressed gas reaching the second cylinder starts expanding,
thereby applying pressure on the front face 422 of the second
piston 420 which causes the second piston 420 to move axially
towards the anvil drive bumper 460. The anvil 430 accordingly moves
axially into the fastener guide 530. The anvil retracting mechanism
450 gets compressed thereby storing energy into the anvil
retracting mechanism 450. In this position, when the releasing of
compressed gas into the second cylinder 400 occurs, the pinion
teeth 2202 of the pinion 2200 still have good engagement with the
rack teeth 2324 of the rack 2300. The engagement of the pinion
teeth 2202 of the pinion 2200 and the rack teeth 2324 of the rack
2300, in the linear forward motion of the rack 2300 and the first
piston 220 provides higher contact ratio between the pinion 2200
and the rack 2300. This higher contact ratio provides the advantage
of substantially reducing the wear on the pinion teeth 2202 of the
pinion 2200 and the rack teeth 2324 of the rack 2300. The pinion
2200 and the rack 2300 maintain a contact ratio of approximately
greater then 0.1 until the valve arrangement 300 releases the
compressed air into the second cylinder 400.
The movement of the first piston 220 creates the timing for opening
of the valve spool 320 of the valve arrangement 300. The first
piston 220 pushes the valve spool 320 to open the valve arrangement
300 before the first piston 220 reaches the first position (top
dead center). The advantage of opening of the valve arrangement 300
while the first piston 220 is still advancing is that the pressure
in the gas chamber 250 cannot force the first piston 220 back.
Additionally, if the valve arrangement 300 opens too early, the
pressure offered by the gas chamber 250 would be insufficient
pressure to drive the second piston 420 for driving the fastener
500 into the substrate 600. Furthermore, if the valve arrangement
300 opens too late, the rack 2300 and first piston 220 starts to
return before the anvil 430 drives the fastener 500 into the
substrate 600, such that the energy for driving the fastener 500 is
lost since the return of the rack 2300 and the first piston 220
allows the gas to expand back into the gas chamber 250.
The opening of the valve arrangement 300 on sufficiently
compressing the air in the gas chamber 250 includes several
parameters that are important for the configurational features of
the valve arrangement 300. The parameters are the pressure drop
through the valve arrangement 300, the opening time of the valve
arrangement 300 and the volume of air contained in gas passageway
360. The valve arrangement 300 in this embodiment is a snap acting
valve having an opening speed of less than 20 milliseconds from
initial cracking to greater then substantially 70 percent of full
flow. The opening time of the valve arrangement 300 is met by
applying an opening force of approximately a minimum of 1.5 to 2
times of the force required to maintain valve arrangement 300 and
more specifically when the valve spool 320 in the closed
position.
As used herein, the opening force is the force applied by the
compressed gas of the gas chamber 250 to open the valve arrangement
300. In one embodiment, the opening force that may drive a standard
18 gage 2'' long fastener, for example, a nail, fully into pine
substrate is the force when the gas in the gas chamber 250 is
compressed to approximately 160 psi with a volume of approximately
1.0 cubic inch. The volume of gas contained in gas passageway 360
should be less than 10 percent of the initial uncompressed volume
of gas in the gas chamber 250, when the first piston 220 is in
first position, for fully driving the fastener.
Accordingly, the valves, which open quickly, fully and do not have
too high volume in the gas passageway, enable driving of the
fastener fully into the substrate. Furthermore, a high Cv (flow
coefficient of a valve and relates the pressure drop across the
valve to the flow through the valve) characteristic and snap action
features of valve arrangement 300 with the low volume of gas
contained within the gas passageway 360 result in a significant
reduction of the compression energy and increase the life of the
power source, such as a battery, by 30 percent. The high Cv valve
arrangement gives a larger flow of gas through a valve arrangement
at a given pressure drop than a low Cv valve arrangement. The
configurational features of the valve arrangement 300 in
combination with the high Cv results in very fast opening speed and
very efficient conversion of the energy of the gas from the gas
chamber 250 through the valve arrangement 300 such that the anvil
430 drives the fastener 500 into the substrate 600 in an efficient
manner.
In one embodiment of the present disclosure, the valve spool 320
weighs approximately 1 oz, a valve return spring 350 is compressed
to approximately 3 lbs, and valve retainers 340 result in an
opening force of approximately 24 lbs. The front face portion 328
of the valve spool 320 has a diameter approximately 0.437 in. The
internal pressure in the gas chamber 250 upon reaching
approximately 160 psi, results in a force of 24 lbs on the diameter
of the front portion 328 of the valve spool 320. This moves the
valve spool 320 past the tipping point 370 (a displacement of
approximately 0.06 inches) at which the maintaining force (less
than 24 lbs) drops to 3 lbs. The tipping point is clearly shown in
FIG. 7 in which the o-ring (not shown) on the valve spool 320 has
not moved past the gas passageway 360 thus leaving the gas under
compression in the gas chamber 250. The o-ring is an elastomeric
element that functions as a sealing member to allow clearance
between the valve spool 320 and the valve body 310. The opening
force on the valve spool 320 is approximately 21 lbs. The
additional stroke of the valve spool 320 to the fully open position
shown in FIG. 8 is 0.5 inches. This distance is traversed in less
then approximately 5 milliseconds, resulting in nearly
instantaneous communication of the compressed gas in the gas
chamber 250 through the gas passageway 360 and to the second
cylinder 400.
Referring now to FIG. 13, illustrated is a longitudinal
cross-sectional view of the fastener driving apparatus 2000,
incorporating the rack and pinion arrangement 2100 and depicting a
completely opened valve arrangement 300. The further continued
rotation of the pinion 2200 causes the rack 2300 and the first
piston 220 to continue proceeding towards the first cylinder end
cap 240 and forcing the gas in the gas chamber 250 to the second
cylinder 400 through the gas passageway 360, which is fully open
(See FIG. 8). This causes the maximum amount of compressed gas in
the gas chamber 250 to be delivered to the second cylinder 400
through the gas passageway 360. The compressed gas in the second
cylinder 400 expands therein and further applies pressure on the
second piston 420 causing it to move axially further towards the
anvil drive bumper 460. The anvil 430 further moves axially into
the fastener guide 530 and applies pressure on the fastener 500
disposed from the fastener feeder into the fastener guide 530. Due
to the applied pressure by the anvil 430, the fastener 500 is
punched into the substrate 600.
Once the rack and pinion arrangement 2100 reaches the second
position, the fastener driving apparatus 2000 almost completes a
single stroke. The single stroke compression enables compressing
the gas in the gas chamber 250 such that the compression exponent
of the air inside the gas chamber 250 is greater than 1. The
compression exponent greater than 1 yields higher gas pressure for
a given compression ratio and increases the volumetric efficiency
of the configurational aspect of the fastener driving apparatus
2000 by allowing more energy to be stored in a volume of gas
compared to the compression done via a normal multi-stroke
compressor in which the heat of compression is lost to the
environment. In the present embodiment, the fastener driving
apparatus 2000 has an efficient design such that the single stoke
operation is sufficiently short (in terms of time) to yield a
compression exponent of approximately 1.1. Further, in the second
position the first return spring 2400 is stretched (energized)
completely due to the further forward linear motion of the rack and
pinion arrangement 2100.
Upon completion of the stroke (i.e. the first piston 220 reaching
the first position) a maximum amount of compressed gas is delivered
to the second cylinder 400. Thereafter, the pressure inside the gas
chamber 250 falls below the pressure applied by the valve return
spring 350 which thereby applies pressure on the valve spool 320
causing the valve spool 320 to return to the closed position. That
is, the valve spool 320 is disposed back into the central hollow
portion 242 of the first cylinder end cap 240. This is illustrated
in FIG. 14, wherein a longitudinal cross-sectional view of the
fastener driving apparatus 2000, incorporating the rack and pinion
arrangement 2100 and depicting the closure of the valve arrangement
300, is shown. The rack 2300 and the first piston 220 moves
linearly from the second position towards the first position by the
pull exerted by the first return spring 2400. In this situation,
check valve 230 on the first piston 220 opens for intake of the gas
into the gas chamber 250 of the first cylinder 200. During the
closure of the valve arrangement 300, the second piston 420 also
retracts to an original position towards the valve arrangement 300.
The anvil 430 coupled to the second piston 420 is also retracted
back from the fastener guide 530. More specifically, the first
position, the second position, and the return to the first position
of the rack and pinion arrangement 2100 constitute a single cycle
of operation for the fastener driving apparatus 2000.
The fastener driving apparatus 2000 further comprises a plurality
of sensors, i.e. a pinion sensor (not shown), that aides the
control circuit 40 in knowing where exactly is the first piston 220
at certain points in the cycle. Further, a rack sensor (not shown)
enables the control circuit 40 in knowing the starting position of
the first piston 220 and that the rack and pinion arrangement 2100
is ready for another cycle. The sensors may also be placed on the
first piston 220, any gear or of the gear reduction 50 or on the
valve arrangement 300. When the control circuit 40 picks up one of
these sensors, the control circuit 40 knows the position of the
first piston 220 within the first cylinder 200. In this embodiment,
when the rack teeth 2324 of the rack 2300 disengage from the pinion
teeth 2202 of the pinion 2200, a sensor (not shown) detects the
disengagement of the teeth with the help of a magnet 2600 disposed
on the pinion 2200, such that the control circuit 40 turns off the
power source 30. The backward motion of the rack 2300 towards the
bumper 2700 preferably is detected by using an additional sensor
(not shown) such that the sensor marks the completion of a cycle
and ready for another cycle.
Further, the disengagement of the rack 2300 and the pinion 2200
move the rack and pinion arrangement 2100 backward. The backward
motion of the rack and pinion arrangement 2100 is movement of the
first piston 220 from the second position towards the first
position. More specifically, the first return spring 2400 enables
backward movement of the rack and pinion arrangement 2100. The
first return spring 2400 does not play a direct part in the
compression of the air in the gas chamber 250 and has a size such
that the total energy of the first return spring 2400 is less then
approximately 15 percent of the energy required to drive the
fastener 500. In this embodiment, the first return spring 2400 is
designed to have total return energy of approximately 0.5 ft lbs on
the first piston 220. The first return spring 2400 is preferably a
constant force spring located external to the first cylinder 200.
The constant force provides more stability and better position
control of the rack 2300 during the cycle.
In the backward movement of the rack and pinion arrangement 2100,
gas is allowed to enter the first cylinder 200 rapidly with the
help of check valve 230. More specifically, the air pushes the
check valve ball away from the sealed position and flows through
the check valve 230 replenishing the gas chamber 250. The
amount/volume of air intake into the gas chamber 250 should be
proportional to the amount of work to be done by the rack and
pinion arrangement 2100, for example, amount of work/energy
required for driving an 18 gage nail.
Furthermore, the excess energy from the rack 2300 is absorbed by
the bumper 2700 disposed at an end of the first return spring 2400.
The bumper 2700 absorbs the kinetic energy caused by the backward
motion of the rack 2300. The bumper 2700 may be preferably made
from an elastomer. The check valve 230 remains open till the time
the pressure in the gas chamber 250 is less then the outside
atmospheric pressure and closes when pressure in the gas chamber
250 increases more than the outside atmospheric pressure. The
intake of gas into the gas chamber 250 continues until the first
piston 220 is about to reach the first position. Once the first
piston 220 reaches the first position within the first cylinder 200
the amount/volume of air intake into the gas chamber 250 is
proportional to the amount of work to be done and the fastener
driving apparatus 2000 is ready for the next cycle of
operation.
In yet another embodiment, the fastener driving apparatus 2000 may
be coupled with a clutch (not shown). Generally the operation
begins with the motor 20 starting to rotate, moving the rack and
pinion arrangement 2100, firing the valve arrangement 300 and then
stopping. If a clutch is used, the motor 20 may be allowed to run
continuously. For example, when a nosepiece (i.e., a fastener guide
530) of the fastener driving apparatus 2000 is positioned against
the substrate 600, the motor 20 may be started. In this way, all
the energy needed is in the motor 20 before transferred to the rack
and pinion arrangement 2100. When the user pulls the start switch
(trigger), this engages the clutch which engages the rack and
pinion arrangement 2100. Because the motor is not starting from a
"dead stop," energy can be extracted right away and much more
quickly. Motors generally have the most power in the midrange of
their operating range of revolutions per minute (RPMs). These
motors deliver no power at the start (as they are not rotating yet)
and are less efficient at lower RPMs than at higher RPMs. If the
fastener driving apparatus 2000 is engaged in this fashion, the
fastener driving apparatus 2000 has a much more responsive feel.
For example, by using the fastener driving apparatus 2000 of the
present invention, the time from a trigger pull to driving an 18
gage fastener may be reduced from about 100 milliseconds to about
50 milliseconds while creating a much more responsive tool feel to
the professional user.
Referring to FIGS. 15-19, in yet another embodiment, the present
invention provides a more compact and ergonomic fastener driving
apparatus. The fastener driving apparatus in this embodiment
configures a compression cylinder placed parallelly along an
expansion cylinder with a valve arrangement disposed over the
compression cylinder and the expansion cylinder. The valve
arrangement is disposed in a manner such that the valve arrangement
acts as a medium for communicating gas between the compression
cylinder and the expansion cylinder.
FIGS. 15-19, show a longitudinal cross-sectional view of a fastener
driving apparatus 3000 illustrating a crankshaft and connecting rod
arrangement 3100. The fastener driving apparatus 3000 comprises a
switch 10; a motor 20; a power source 30; a control circuit 40; a
gear reduction mechanism 50; a linear motion converter, for example
a crankshaft and connecting rod arrangement 3100 in this
embodiment; a first cylinder 200; a valve arrangement 300 and a
second cylinder 400. As used herein, the first cylinder 200 is the
compression cylinder wherein a gas is compressed and the second
cylinder 400 is the expansion cylinder wherein the compressed gas
is allowed to expand. The fastener driving apparatus 3000 is
capable of driving a fastener 500 into a substrate 600 by utilizing
power of a gas compressed within the first cylinder 200. The
compressed gas is communicated to the second cylinder 400 through
the valve arrangement 300 and enables the compressed gas to expand
in the second cylinder 400, thereby applying pressure to the
fastener 500 for driving the fastener 500 into the substrate
600.
When a user presses the start switch 10, power from the power
source 30 is directed to the motor 20 through the control circuit
40 in a manner such that the motor 20 generates a rotational
motion. The rotational motion generated by the motor 20 is
communicated to the linear motion converter, which is the
crankshaft and connecting rod arrangement 3100 in this embodiment,
using the gear reduction mechanism 50. The gear reduction mechanism
50 comprises a plurality of gears (not shown) that transfers the
rotational motion of a shaft (not shown) of the motor 20 to the
crankshaft and connecting rod arrangement 3100. The crankshaft and
connecting rod arrangement 3100 comprises a crankshaft 3200 and a
connecting rod 3300 coupled to the crankshaft 3200 (See FIGS.
15A-19A). The crankshaft 3200 comprises a first portion 3210, a
middle portion 3220 and a second portion 3230. The first portion
3210, the middle portion 3220 and the second portion 3230 are
configured in a manner such that the configuration constitutes a
`U` shaped structure. The crankshaft 3200 is coupled to the
connecting rod 3300 about the middle portion 3220.
The crankshaft 3200 is further coupled to a body 3400 of the
fastener driving apparatus 3000 about the first portion 3210 of the
crankshaft 3200 and to the gear reduction mechanism 50 about the
second portion 3230 of the crankshaft 3200. The connecting rod 3300
has a first end portion (not shown) coupling the first piston 220
using a connector 3310 and a second end portion (not shown)
coupling the middle portion 3220 of the crankshaft 3200. More
specifically, the first portion 3210 and the second portion 3230
have a horizontal protruding members (not shown) which are
responsible for the coupling of the first portion 3210 with the
body 3400 of the fastener driving apparatus 3000 and the second
portion 3230 with the gear reduction mechanism 50. Further, one of
the gears of the gear reduction mechanism 50 is coupled to the
second portion 3230 of the crankshaft 3200 for transmitting the
rotational motion generated by the motor 20 to the crankshaft and
connecting rod arrangement 3100 which enables the movement of the
crankshaft and connecting rod arrangement 3100 for the operation of
the fastener driving apparatus 3000.
The first cylinder 200 comprises a cylinder guide (not shown) and a
first piston 220 disposed therein. The first piston 220 is coupled
to connecting rod 3300 in a manner, such that, the rotational
motion of the crankshaft 3200 is converted to linear reciprocal
motion of the first piston 220 within the first cylinder 200. The
first cylinder 200 further comprises a first cylinder end cap 240
towards an end of the first cylinder 200. The first piston 220
defines a gas chamber 250 within the first cylinder 200 and between
the first cylinder end cap 240 and the first piston 220. The gas
chamber 250 is capable of accommodating gas therein. The first
cylinder 200 further comprises check valves 230 and 232 disposed on
the first piston 220. The check valves 230 and 232 are configured
to operate in a manner such that when the check valves 230 and 232
are in an open position, the check valves 230 and 232 enables the
entry of gas into the gas chamber 250 of the first cylinder 200 and
when in a closed position, the check valves 230 and 232 prevents
any exit of gas from the gas chamber 250. Additionally, the first
piston 220 is disposed with a magnet 3500. A sensor 3600 disposed
on the valve arrangement 300 in combination with the magnet 3500
enables in knowing the various positions of the first piston 220 in
the first cylinder 200 during the reciprocal movement of the first
piston 220.
The first cylinder end cap 240 is coupled to the valve arrangement
300. Referring to FIGS. 6-9, the valve arrangement 300 is
illustrated in detail. The first cylinder end cap 240 has a central
hollow portion 242. The valve arrangement 300 comprises a valve
body 310 having a central groove 312 extending along a longitudinal
axis X-X of the valve body 310. The central groove 312 conforms to
the central hollow portion 242 of the first cylinder end cap 240 at
the front end portion, while the rear end portion of the central
groove 312 is closed. A valve spool 320 is seated up against the
valve body 310 within the central groove 312 along the longitudinal
axis X-X and is capable of reciprocating linearly within the
central groove 312. In one embodiment, the valve spool 320 has a
cylindrical body having a stepped structure configured by a primary
body portion 322 and a concentric secondary body portion 324.
The primary body portion 322 has a diameter greater than a diameter
of the secondary body portion 324. The primary body portion 322
gradually extends into the secondary body portion 324 in a manner
such that the graduation of the primary body portion 322 into the
secondary body portion 324 configures a chamfered portion 326 (see
FIG. 8). The valve spool 320 reciprocates within the central groove
312 of the valve body 310 along the longitudinal axis X-X. The
valve spool 320 further has a front face portion 328, a rear face
portion 330 and a valve spool stem 332 extending outwardly from the
front face portion 328 along a longitudinal axis of the valve spool
320. In an initial closed position, the front face portion 328 is
positioned in the central hollow portion 242 of the first cylinder
end cap 240 in a manner, such that, the front face portion 328
closes the central hollow portion 242, while the valve spool stem
332 extends into the gas chamber 250 of the first cylinder 200.
The valve arrangement 300 further comprises a pair of valve
retainers 340 positioned in an opposed relationship laterally along
the central groove 312 of the valve body 310. In one embodiment,
each valve retainer 340 is in the form of a cup 342 and retention
ball 344. In the initial closed position, when the valve spool 320
is closing the central hollow portion 242 of the first cylinder end
cap 240, the valve spool 320 is retained in such a position by the
valve retainers 340. The valve retainers 340 are positioned in a
manner such that the retention balls 344 are disposed at the
chamfered portion 326 of the valve spool 320, thereby applying
pressure on the valve spool 320 and preventing the valve spool 320
to deviate from the position closing the central hollow portion 242
of the first cylinder end cap 240.
Additionally, the valve arrangement 300 comprises a valve return
spring 350 disposed within the central groove 312 and towards the
rear end portion of the central groove 312. The rear face portion
330 of the valve spool 320 is disposed on the valve return spring
350. The valve arrangement 300 further comprises a gas passageway
360 configured from the central groove 312 of the valve arrangement
300 and connected to the second cylinder 400. In the initial closed
position, when the front face portion 328 of the valve spool 320 is
disposed on the central hollow portion 242, the primary body
portion 322 closes the gas passageway 360. The gas passageway 360
is configured to define a duct for communicating the gas from the
gas chamber 250 of the first cylinder 200 to the second cylinder
400.
The second cylinder 400 comprises a cylinder guide 410 and a second
piston 420 disposed there within. The second piston 420 has a front
face 422 and a rear face 424. The rear face 424 of the second
piston 420 is coupled to an anvil 430 using a connector 440. The
anvil 430 extends along a longitudinal axis of the second cylinder
400 into a fastener guide 530. The anvil 430 is capable of linearly
moving through the second cylinder 400 and the fastener guide 530.
The fastener guide 530 is configured to receive the fastener 500
from a fastener feeder 550 and the linearly moving anvil 430 is
capable of applying pressure to the fastener 500 in the fastener
guide 530.
The second cylinder 400 further comprises an anvil retracting
mechanism (return spring) 450 and an anvil drive bumper 460. The
anvil drive bumper 460 is disposed at an end of the second cylinder
400 away from an end having the valve arrangement 300. The anvil
retracting mechanism 450 is coupled to the rear face 424 of the
second piston 420 at one end and to the anvil drive bumper 460 at
another end. In a situation when the second cylinder 400 has not
received the compressed gas from the first cylinder 200, the second
piston 420 is positioned towards the valve arrangement 300 and the
anvil retracting mechanism 450 is in a relaxed position i.e. the
anvil retracting mechanism 450 is not compressed. Such a position
is also referred to as the load-free position. In another
embodiment, the anvil retracting mechanism comprises a bungee
retraction (not shown), whereby the bungee is attached to the front
face 422 of the second piston 420 and to the end of the second
cylinder 400 that has the valve arrangement 300. In yet another
embodiment of the present invention, the retraction of the anvil
may be accomplished by air power in the manner employed by standard
pneumatic nailers.
Referring now to FIG. 15, illustrated is a longitudinal
cross-sectional view of the fastener driving device 3000,
incorporating the crankshaft and connecting rod arrangement 3100
moving from a first position (top dead center) to a second position
(bottom dead center). Upon pressing a start switch 10, causes power
to be directed from the power source 30 to the motor 20 through the
control circuit 40 for starting an operational cycle of the
fastener driving device 3000. The operational cycle is the various
operational phases involved in the operation of the fastener
driving device 3000 for driving a single fastener into a substrate.
The control circuit 40 may be any apparatus for connecting power to
the motor 20 for the purpose of initiating an operational cycle of
the fastener driving device 3000 and then removing the power to the
motor 20 after the operational cycle of the fastener driving device
3000 has substantially completed.
The rotational motion of the crankshaft 3200 causes the first
piston 220 to move linearly within the first cylinder 200 from the
first position towards the second position. More specifically, the
shaft of the motor 20 which is coupled to the gear reduction
mechanism 50 transmits the rotational motion of the motor 20 to the
gear reduction mechanism 50 that further transmitted to the
crankshaft 3200 which is coupled to the gear reduction mechanism 50
about the second portion 3230. In the above mentioned condition the
crankshaft 3200 rotates in the clockwise direction and the position
of the crankshaft and connecting rod arrangement 3100 with respect
to first piston 220 is clearly illustrated in the FIG. 15A. This
movement of the piston causes the check valves 230 and 232 of the
first piston 220 to open for intake of the gas into the gas chamber
250 thereby closing the central hollow portion 242 and the gas
passageway 360. The first piston 220 starts moving from the first
position towards the second position, such that, the gas chamber
250 of the first cylinder 200 is occupying air through the open
check valves 230 and 232 disposed on the first piston 220.
Referring now to FIG. 16, illustrated is a longitudinal
cross-sectional view of the fastener driving apparatus 2000,
incorporating the crankshaft and connecting rod arrangement 3100 in
the second position. The second position as used herein refers to
the position of the first piston 220 at bottom dead center and away
from the first cylinder end cap 240. In the above mentioned
condition, the crankshaft 3200 (coupled to the connecting rod 3300)
further rotates in clockwise direction, such that, the first piston
220 reaches the second position and the position of the crankshaft
and connecting rod arrangement 3100 with respect to first piston
220 is clearly illustrated in the FIG. 16A. The movement of the
first piston 220 towards the second position closes the check
valves 230 and 232. The closing of the check valves 230 and 232
prevents any exit of gas from the gas chamber 250. The gas chamber
250 is now occupied with a volume of gas proportional to the amount
of work to be done by the first piston 220 within the first
cylinder 200. The gas used is the atmospheric air at atmospheric
pressure which thereby simplifies the design of the fastener
driving apparatus 3000, as using air greater than atmospheric
pressure might otherwise require another pre-compressor to increase
the pressure of the air inside the gas chamber 250.
Referring now to FIG. 17, illustrated is a longitudinal
cross-sectional view of the fastener driving apparatus 3000,
incorporating the crankshaft and connecting rod arrangement 3100 in
an intermediate position, between the first position and the second
position. More specifically, the further clockwise rotation of the
crankshaft 3200 imparts movement to the connecting rod 3300, such
that, the first piston 220 begins to move linearly from the second
position to the intermediate position within the first cylinder
200. The position of the crankshaft and connecting rod arrangement
3100 with respect to first piston 220 is clearly illustrated in the
FIG. 17A. At the intermediate position the air inside the gas
chamber 250 of the first cylinder 200 is compressed with a linear
forward motion of the first piston 220.
In the above mentioned condition, the check valves 230 and 232 are
in the closed position, preventing any exit of gas from the gas
chamber 250. Further, in the intermediate position the valve spool
320 is disposed in the central hollow portion 242 of the first
cylinder end cap 240 in a manner such that the valve spool 320
closes the central hollow portion 242 and the gas passageway 360.
The force offered by the compressed gas within the gas chamber 250
to the valve spool 320 is less than the force applied by valve
return spring 350 on the valve spool 320. In such a position, the
valve arrangement 300 is more specifically illustrated in FIG. 6,
wherein the valve retainers 340 and the retention balls 344 are
disposed at the chamfered portion 326 of the valve spool 320. Such
positioning of the retention balls 344 applies pressure on the
valve spool 320 and prevents the valve spool 320 to deviate from
the position closing the central hollow portion 242 of the first
cylinder end cap 240. The gas in the gas chamber 250 is held
between the first piston 220 and the valve arrangement 300 until
the valve arrangement 300 opens.
Referring to FIG. 18, illustrated is a longitudinal cross-sectional
view of the fastener driving apparatus 3000, incorporating the
crankshaft and connecting rod arrangement 3100 moving from the
intermediate position towards the first position with a partially
opened valve arrangement 300. The valve arrangement 300 opens
either when the force offered by the compressed gas within the gas
chamber 250 to the valve spool 320 has exceeded the force applied
by valve return spring 350 on the valve spool 320 or when the first
piston 220 strikes the valve spool stem 332 of the valve spool
320.
In the above mentioned condition, the valve arrangement 300 is
partially opened with the force of the compressed gas within the
gas chamber 250. More specifically, the further clockwise rotation
of the crankshaft 3200 imparts movement to the connecting rod 3300
such that the first piston 220 begins to move linearly from the
intermediated position towards the first position compressing the
gas in the gas chamber 250 to an extent that the valve arrangement
300 opens. The position of the crankshaft and connecting rod
arrangement 3100 with respect to first piston 220 is clearly
illustrated in the FIG. 18A. In such a situation, the gas inside
the gas chamber 250 pushes the valve spool 320 to move linearly
inside the central groove 312 of the valve body 310 in a manner
such that the valve spool 320 opens central hollow portion 242. The
position of the valve arrangement in this situation may be more
specifically referred to in FIG. 7, when the valve spool 320 opens
the central hollow portion 242, the retention balls 344 cross a
tipping point 370. The tipping point 370, as used herein, refers to
a point of contact between the retention balls 344 and the valve
spool 320, when the valve retainers 340 and the retention balls 344
provide minimal resistance to the linear movement of the valve
spool 320, thereby resulting in an opening of the gas passageway
360.
After the tipping point 370, the valve retainers 340 only provide a
frictional force to the valve spool 320. This frictional force is
far less than the direct force afforded by the valve retainers 340
on the valve spool 320. In the embodiment shown, once the retention
balls 344 ride up the chamfered portion 326 on the valve spool 320,
the force from the retention balls 344 to maintain the valve spool
320 in its position changes from 45 degrees (or the angle of the
chamfered portion 326) to 90 degrees, which is perpendicular to the
movement of the valve spool 320. This essentially removes the
retention balls 344 and the valve retainers 340 from retaining the
valve spool 320, as the valve retainers 340 acting perpendicular to
the valve spool movement and can no longer restrain the valve spool
320. The only force maintaining the valve spool 320 in the closed
position is the force from the valve return spring 350. This is
substantially less than the compressed gas pressure that is applied
to a face of the valve spool 320, thus the valve spool 320 snaps
open.
Further, this enables the compressed gas within the gas chamber 250
to be released into the second cylinder 400 through the valve
arrangement 300 and, more specifically, through the gas passageway
360. The compressed gas reaching the second cylinder 400 starts
expanding, thereby applying pressure on the front face 422 of the
second piston 420 which causes the second piston 420 to move
axially towards the anvil drive bumper 460. The anvil 430
accordingly moves axially into the fastener guide 530 for applying
pressure on the fastener 500 disposed within the fastener guide
530. The fastener 500 further moves towards the substrate 600 when
the anvil 430 applies pressure on the fastener 500. The axial
movement of the second piston 420 towards the anvil drive bumper
460 compresses the anvil retracting mechanism 450 thereby storing
energy into the anvil retracting mechanism 450.
Referring now to FIG. 19, illustrated is a longitudinal
cross-sectional view of the fastener driving apparatus 3000,
incorporating the crankshaft and connecting rod arrangement 3100 in
the first position with a completely opened valve arrangement 300.
In this conditioned, the first piston 220 continue to proceed
towards the first cylinder end cap 240 thereby further compressing
the gas in the gas chamber 250. This results in a further increase
in the pressure in the gas chamber 250, causing the valve spool 320
to move further within the central groove 312 and completely open
the gas passageway 360 of the valve arrangement 300. More
specifically, the further clockwise rotation of the crankshaft 3200
imparts movement to the connecting rod 3300, such that, the first
piston 220 reaches the first position by compressing the gas in the
gas chamber 250 to an extent that the valve arrangement 300
completely opens.
The position of the crankshaft and connecting rod arrangement 3100
with respect to first piston 220 is clearly illustrated in the FIG.
19A, The complete opening of the valve arrangement 300 causes the
maximum amount of compressed gas in the gas chamber 250 to be
delivered to the second cylinder 400 through the gas passageway
360. The compressed gas in the second cylinder 400 expands therein
and further applies pressure on the second piston 420 causing it to
move axially further towards the anvil drive bumper 460. The anvil
430 further moves axially into the fastener guide 530 and applies
pressure on the fastener 500 disposed from the fastener feeder 550
into the fastener guide 530. Due to the applied pressure by the
anvil 430, the fastener 500 is punched into the substrate 600.
Once the crankshaft and connecting rod arrangement 3100 reaches the
first position, the fastener driving apparatus 3000 almost
completes the operational cycle in a single stroke. The single
stroke compression enables in compressing the gas inside the gas
chamber 250, such that, the compression exponent of the gas inside
the gas chamber 250 is greater then 1. In the present embodiment,
the fastener driving apparatus 3000 has an efficient design, such
that, the single stoke operation is sufficiently short (in terms of
time) to yield a compression exponent of approximately 1.1.
The fastener driving apparatus 3000 further comprises a plurality
of sensors (not shown) that aides the control circuit 40 in knowing
where exactly is the first piston 220 at certain points in the
operational cycle. The sensors may be placed on the first piston
220, any gear or of the gear reduction mechanism 50 or on the valve
arrangement 300. When the control circuit 40 picks up one of these
sensors, the control circuit 40 knows the position of the first
piston 220 within the first cylinder 200. In this embodiment, the
various positions of the first piston 220 within the first cylinder
200 is determined with the help of the magnet 3500 disposed on the
first piston 220 and the sensor 3600 disposed on the valve
arrangement 300, such that, the control circuit 40 turns off the
power source 30 when the first piston 220 reaches the first
position.
Further, in the above mentioned conditioned the second piston 420
compresses the anvil retracting mechanism 450 thereby storing more
energy into the anvil retracting mechanism 450. Furthermore, the
excess energy from the second piston 420, the connector 440 and the
anvil 430 is absorbed by the anvil drive bumper 460 disposed at the
end of the second cylinder 400. The anvil drive bumper 460 absorbs
the kinetic energy caused by the axial movement of the second
piston 420, the connector 440 and the anvil 430 towards the anvil
drive bumper 460 when the valve arrangement 300 is in fully opened
conditioned. The anvil drive bumper 460 may be preferably made from
an elastomer. Once the first piston 220 reaches the first position
within the first cylinder 200 the fastener driving apparatus 3000
is ready for the next cycle of operation.
In yet another embodiment, the fastener driving apparatus 3000 may
be coupled with a clutch (not shown). Generally the operation
begins with the motor 20 starting to rotate, moving the crankshaft
and connecting rod arrangement 3100, firing the valve arrangement
300 and then stopping. If a clutch is used, the motor 20 may be
allowed to run continuously. For example, when a nosepiece (i.e., a
fastener guide 530) of the fastener driving apparatus 3000 is
positioned against the substrate 600, the motor 20 may be started.
In this way, all the energy needed is in the motor 20 before being
transferred to the crankshaft and connecting rod arrangement 3100.
When the user pulls the start switch (trigger), this engages the
clutch which in turn engages the crankshaft and connecting rod
arrangement 3100. Because the motor 20 is not starting from a "dead
stop," energy can be extracted right away and much more
quickly.
Motors generally have the most power in the midrange of their
operating range of revolutions per minute (RPMs). These motors
deliver no power at the start (as they are not rotating yet) and
are less efficient at lower RPMs than at higher RPMs. If the
fastener driving apparatus 3000 is engaged in this fashion, the
fastener driving apparatus 3000 has a much more responsive feel.
For example, by using the fastener driving apparatus 3000 of the
present invention, the time from a trigger pull to driving an 18
gage fastener may be reduced from about 100 milliseconds to about
50 milliseconds while creating a much more responsive tool feel to
the professional user.
In yet another embodiment, the present the present invention
provides a fastener driving apparatus capable of driving larger
fasteners. The design of such a fastener driving apparatus
generally requires a large amount of starting gas. To meet the
requirement of the large amount of starting gas, the present
invention incorporates a slider crank arrangement to stroke more
than once in a first cylinder of the fastener driving apparatus for
creating more compressed gas. For example, if a fastener such as a
nail requires 14 cubic inch of gas compressed to a compression
ratio of 8:1, then it would be advantageous to use the slider crank
arrangement with the first cylinder volume slightly larger than
half of the required volume and to stroke the slider crank
arrangement twice.
To accomplish this, the first cylinder is to be configured having a
primary gas chamber and a secondary gas chamber. The secondary gas
chamber is in close proximity with the primary gas chamber, with
the chambers being separated by a check valve. The primary gas
chamber is used for accommodating the slider crank arrangement for
compressing the gas within the primary gas chamber and the
secondary gas chamber is used for storing the compressed gas of the
primary gas chamber with a compression exponent greater than unity.
The first cylinder is coupled to a second cylinder through a valve
arrangement disposed between the first cylinder and the second
cylinder. In one embodiment, the valve arrangement is cam driven
valve which enables in communicating compressed gas between the
first cylinder and the second cylinder upon compressing the gas in
the first cylinder.
Referring to FIGS. 20-28, in another embodiment, a longitudinal
cross-sectional view of a fastener driving apparatus 4000
incorporating a cam arrangement 4200 coupled to a slider crank
arrangement 4100, is shown. The fastener driving apparatus 4000
comprises a switch 10; a motor 20; a power source 30; a control
circuit 40; a gear reduction mechanism 50; a linear motion
converter, for example a slider crank arrangement 4100; a first
cylinder 200, a valve arrangement 4300 and a second cylinder 400.
The fastener driving apparatus 4000 is capable of driving a
fastener 500 into a substrate 600 by utilizing power of a gas
compressed within the first cylinder 200. The compressed gas is
communicated to the second cylinder 400 through the valve
arrangement 4300 and enables the compressed gas to expand in the
second cylinder 400 thereby applying pressure to the fastener 500
for driving the fastener 500 into the substrate 600.
When a user presses the start switch 10, power from the power
source 30 is directed to the motor 20 through the control circuit
40 in a manner such that the motor 20 generates a rotational
motion. The rotational motion generated by the motor 20 is
communicated to the slider crank arrangement 4100, using the gear
reduction mechanism 50. The gear reduction mechanism 50 comprises a
plurality of gears (not shown) that transfers the rotational motion
of a shaft (not shown) of the motor 20 to the slider crank
arrangement 4100 which is further transferred to the cam
arrangement 4200.
The slider crank arrangement 4100 comprises a crank wheel 4500
coupled to a crank link 4400 about a first end 132. The crank wheel
4500 is coupled to a worm gear 110 of the gear reduction mechanism
50 in a manner such that a rotational motion of the worm gear 110
is transferred into a rotational motion of the crank wheel 4500.
The rotational motion of the crank wheel 4500 further imparts
movement to the crank link 4400. The worm gear 110 receives the
rotational motion from the motor 20 through the gear reduction
mechanism 50. Further, the rotational motion of the crank wheel
4500 is transferred to the cam arrangement 4200 for operating the
valve arrangement 4300.
The first cylinder 200 comprises a first cylinder guide 210 and a
first piston 220 capable of reciprocally movable within the first
cylinder 200. The first piston 220 is coupled to the crank link
4400 about a second end 134 of the crank link 4400 using a
connector 136 in a manner such that the rotational motion of the
worm gear 110 and the crank wheel 4500 is converted to a linear
reciprocal motion of the first piston 220 within the first cylinder
200 using the crank link 4400. The first cylinder 200 further
comprises a first cylinder end cap 240 disposed about a first end
of the first cylinder 200. The first piston 220 defines a gas
chamber within the first cylinder 200 and between the first
cylinder end cap 240 and the first piston 220.
The gas chamber comprises a separator 4270 dividing the gas chamber
into a primary gas chamber 4250 and a secondary gas chamber 4260.
The primary gas chamber 4250 and the secondary gas chamber 4260 are
capable of accommodating gas therein. The primary gas chamber 4250
is inline with the secondary gas chamber 4260 with the separator
4270 disposed between the primary gas chamber 4250 and the
secondary gas chamber 4260. More specifically, the first piston 220
and the separator 4270 between the first cylinder guide 210
configures the primary gas chamber 4250; and the first cylinder end
cap 240 and the separator 4270 between the first cylinder guide 210
configures the secondary gas chamber 4260. Furthermore, the first
piston 220 is capable of reciprocally moving within the primary gas
chamber 4250.
In an embodiment, the first cylinder 200 further comprises a first
check valve 4230 disposed on the first piston 220 and a second
check valve 4232 disposed on the separator 4270. The first check
valve 4230 operates in a manner such that, when the first check
valve 4230 is in an open position, the first check valve 4230
enables the entry of gas into the primary gas chamber 4250.
Alternatively, when in a closed position, the first check valve
4230 prevents any exit of gas from the primary gas chamber 4250.
The second check valve 4232 operates in a manner such that, when
the pressure in the primary gas chamber 4250 exceeds the pressure
of the secondary gas chamber 4260 the second check valve 4232 is in
an open position enabling the entry of gas into the secondary gas
chamber 4260 from the primary gas chamber 4250. Additionally, in a
closed position, when the pressure of the secondary gas chamber
4260 exceeds the pressure of the primary gas chamber 4250, the
second check valve 4232 prevents any exit of gas from the secondary
gas chamber 4260 to the primary gas chamber 4250.
The first cylinder end cap 240 is coupled to the valve arrangement
4300. Referring to FIGS. 29-32, the valve arrangement 4300 is
illustrated in detail. The first cylinder end cap 240 has a central
hollow portion 242. The valve arrangement 4300 comprises a valve
body 310 having a central groove 312 extending along a longitudinal
axis X-X of the valve body 310. The central groove 312 conforms to
the central hollow portion 242 of the first cylinder end cap 240 at
the front end portion, while the rear end portion of the central
groove 312 has a hole (not shown). A valve spool 320 is seated up
against the valve body 310 within the central groove 312 along the
longitudinal axis X-X and is capable of reciprocating linearly
within the central groove 312. In one embodiment, the valve spool
320 has a cylindrical body having a stepped structure configured by
a primary body portion 322 and a concentric secondary body portion
324.
The primary body portion 322 has a diameter greater than a diameter
of the secondary body portion 324. The primary body portion 322
gradually extends into the secondary body portion 324 in a manner
such that the graduation of the primary body portion 322 into the
secondary body portion 324 configures a chamfered portion 326 there
between (see FIG. 30). The valve spool 320 reciprocates within the
central groove 312 of the valve body 310 along the longitudinal
axis X-X. The valve spool 320 further has a front face portion 328,
a rear face portion 330 and a valve spool stem 332 extending
outwardly from the rear face portion 330 along a longitudinal axis
of the valve spool 320. The valve spool stem 332 passes through the
hole disposed on the rear end portion of the central groove 312 and
couples to the cam arrangement 4200. In an initial closed position,
the front face portion 328 of the valve spool 320 is positioned in
the central hollow portion 242 of the first cylinder end cap 240 in
a manner such that, the front face portion 328 closes the central
hollow portion 242.
The valve arrangement 4300 further comprises a pair of valve
retainers 340 positioned in an opposed relationship laterally along
the central groove 312 of the valve body 310. In one embodiment,
each valve retainer 340 is in the form of a cup 342 and retention
ball 344. In the initial state, when the valve spool 320 is closing
the central hollow portion 242 of the first cylinder end cap 240,
the valve spool 320 is retained in such a position by the valve
retainers 340. The valve retainers 340 are positioned in a manner
such that the retention balls 344 are disposed at the chamfered
portion 326 of the valve spool 320, thereby applying pressure on
the valve spool 320 and preventing the valve spool 320 to deviate
from the position closing the central hollow portion 242 of the
first cylinder end cap 240.
Additionally, the valve arrangement 4300 comprises a valve return
spring 350 disposed within the central groove 312 and towards the
rear end portion of the central groove 312. The rear face portion
330 of the valve spool 320 is disposed on the valve return spring
350. The valve arrangement 4300 further comprises a gas passageway
360 configured from the central groove 312 of the valve arrangement
4300 and extends to the second cylinder 400. In the initial closed
position, when the front face portion 328 of the valve spool 320 is
disposed on the central hollow portion 242, the primary body
portion 322 substantially closes the gas passageway 360. The gas
passageway 360 is configured to define a duct for communicating the
gas from the secondary gas chamber 4260 to the second cylinder 400
through the valve arrangement 4300 with the help of cam arrangement
4200.
The cam arrangement 4200 has a first end coupled to the crank wheel
4500 of the slider crank arrangement 4100 and a second end coupled
to the valve spool stem 332 of the valve spool 320. The cam
arrangement 4200 enables in linear reciprocal movement of the valve
spool 320 within the central groove 312 in a manner such that, the
cam arrangement 4200 enables the opening and closing of the valve
arrangement 4300. The cam arrangement 4200 comprises a cam 4210
coupled to the crank wheel 4500. The cam 4210 is coupled to a
plurality of cam links 4220 for transferring the movement of the
cam 4210 to the valve spool stem 332.
More specifically, the cam 4210 is coupled to the slider crank
arrangement 4100 in a manner, such that, the rotation of the cam
4210 is determined by the number of strokes of the first piston 220
used for compressing the gas in the primary gas chamber 4250. In
the present embodiment, two strokes are used to compress the gas in
the primary gas chamber 4250. Thus, the cam 4210 is allowed to make
one revolution for every two revolutions of the crank wheel 4500
(i.e. two strokes of the slider crank arrangement 4100). The
completion of one revolution of the cam 4210 pulls the valve spool
stem 332 for linearly moving the valve spool 320 from the initial
closed position to an open position and thereby opening the gas
passageway 360, such that, the opening of the gas passageway 360
results in the communication of gas between the first cylinder 200
and the second cylinder 400.
The second cylinder 400 comprises a second cylinder guide 410 and a
second piston 420 disposed there within. The second piston 420 has
a front face 422 and a rear face 424. The rear face 424 of the
second piston 420 is coupled to an anvil 430 using a connector 440.
The anvil 430 extends along a longitudinal axis of the second
cylinder 400 into a fastener guide 530. The anvil 430 is capable of
linearly moving through the second cylinder 400 and the fastener
guide 530. The fastener guide 530 is configured to receive a
fastener 500 from a fastener feeder 550 and the linearly moving
anvil 430 is capable of applying pressure to the fastener 500 in
the fastener guide 530.
The second cylinder 400 further comprises an anvil retracting
mechanism (return spring) 450 and an anvil drive bumper 460. The
anvil drive bumper 460 is disposed at an end of the second cylinder
400 away from an end having the valve arrangement 4300. The anvil
retracting mechanism 450 is coupled to the rear face 424 of the
second piston 420 at one end and to the anvil drive bumper 460 at
another end. In a situation when the second cylinder 400 has not
received the compressed gas from the secondary gas chamber 4260,
the second piston 420 is positioned towards the valve arrangement
4300 and the anvil retracting mechanism 450 is in a relaxed
position i.e. the anvil retracting mechanism 450 is not compressed.
Such a position is also referred to as the load-free position.
An operational cycle of the fastener driving apparatus 4000 may
comprise a plurality of strokes of the first piston 220 within the
primary gas chamber 4250. The plurality of strokes of the first
piston 220 compresses the gas in the primary gas chamber 4250 and
then the compressed gas is transferred to the secondary gas chamber
4260 through the second check valve 4232 and stored therein. The
operation of the fastener driving apparatus 4000 mainly depends on
a compression exponent of the compressed gas stored in the
secondary gas chamber 4260.
Additionally, the compression exponent depends on the number of
strokes of the first piston 220. The plurality of strokes lowers
the compression exponent, since; the plurality of strokes takes
more time due to the 180 degrees of the strokes that are used to
replenish the gas in the primary gas chamber 4250 and with the
passage of time the compressed gas stored in the secondary gas
chamber 4260 cools, thereby resulting in decreasing the compression
exponent of the compressed gas in the secondary gas chamber 4260.
The compression exponent is related to the pressure and temperature
of the compressed gas. For example, a given volume of gas with a
compression exponent of 1.3 has a higher temperature than the same
volume of air having a compression exponent of 1.2. The higher
temperature and pressure enables in storing more energy in the
compressed gas stored in the secondary gas chamber 4260.
The operational cycle of the fastener driving apparatus 4000 is the
various operational stages involved in driving a single fastener
500 into the substrate 600. The present embodiment of the fastener
driving apparatus 4000 is only beneficial if the gas in the
secondary gas chamber 4260 remains compressed with an exponent
greater than 1.0. The advantage of the present embodiment is lost
if the compressed gas is allowed to cool and returning the
compression exponent to 1.0 or less. Thereby, to maintain a
compression exponent greater than 1.0, it is advantageous to limit
the number of strokes of the slider crank arrangement 4100. It is
preferred to keep the number of strokes of the first piston 220 to
be less than 5.
In the present embodiment, the operational cycle of the fastener
driving apparatus 4000 comprises two stokes of the first piston 220
in the primary gas chamber 4250. The two strokes of the first
piston 220 involve a first stroke and a second stroke. The first
stroke and the second stroke are responsible for compressing the
gas in the primary gas chamber 4250 such that the compressed gas is
communicated to the secondary gas chamber 4260 wherein the
compression exponent of the gas in the secondary gas chamber is
greater than 1.05. Further, the functioning of the fastener driving
apparatus 4000 requires the compressed gas having the compression
exponent greater than 1.05 to be transferred and stored in the
secondary gas chamber 4260.
The first stroke comprises moving the first piston 220 from a first
position towards a second position which enables in opening the
first check valve 4232 for intake of gas into the primary gas
chamber 4250 (the second check valve 4232 and the valve arrangement
4300 are in closed position); at the second position enabling the
closure of the first check valve 4230 and storing gas within the
primary gas chamber 4250; moving the first piston from the second
position towards the first position and enabling compressing the
gas in the primary gas chamber 4250; and upon substantially nearing
the first position, enabling the second check valve 4232 to open
causing the compressed gas in the primary gas chamber 4250 to be
transferred to the secondary gas chamber 4260. As used herein the
first position refers to the position of the first piston 220
within the first cylinder 200 near to the separator 4270 and the
second position refers to the position of the first piston 220 near
to the slider crank arrangement 4100 towards the bottom dead center
of the first cylinder 200.
The second stroke comprises moving the first piston 220 from a
first position towards a second position which enables in opening
the first check valve 4232 for intake of gas into the primary gas
chamber 4250 (the second check valve 4232 and the valve arrangement
4300 are in closed position); at the second position enabling the
closure of the first check valve 4230 and storing gas within the
primary gas chamber 4250; moving the first piston from the second
position towards the first position and enabling compressing the
gas in the primary gas chamber 4250; and upon substantially nearing
the first position, enabling the second check valve 4232 to open
causing the compressed gas in the primary gas chamber 4250 to be
transferred to the secondary gas chamber 4260 and wherein the valve
arrangement 4300 is opened to allow the compressed gas to expand in
the second cylinder 400 thereby causing the second piston 420 to
move and enable the anvil 430 to drive the fastener 500 into the
substrate 600.
Referring to FIGS. 20-23, the first stroke of the fastener driving
apparatus 4000 incorporating the cam arrangement 4200 and the
slider crank arrangement 4100 is shown. In the first stroke, when
the start switch 10 is switched ON, power is directed from the
power source 30 to the motor 20 through the control circuit 40. The
control circuit 40 may be any apparatus for connecting power to the
motor 20 for the purpose of initiating the operational cycle of the
fastener driving apparatus 4000 and then removing the power to the
motor 20 after the operational cycle of the fastener driving
apparatus 4000 has substantially completed.
Preferably, the gas used is the atmospheric air at atmospheric
pressure thereby avoiding the usage of any pre-compressor for
pressurizing the intake air. More specifically, referring to FIG.
20, a starting of the first stroke is shown, when the first piston
220 is moving from the first position to an intermediate position.
Upon receiving power from the power source 30, the motor 20 directs
the shaft (not shown) to rotate, transferring energy through the
gear reduction 50 and worm gear 110 to the slider crank arrangement
4100 of the fastener driving apparatus 4000. More specifically, the
worm gear 110 (coupled to crank wheel 4500) rotates the crank wheel
4500 such that the crank wheel 4500 starts rotating (either
clockwise or counterclockwise), causing the first piston 220 to
move linearly away from separator 4270 (from the first position)
within the first cylinder 200.
At the start of the first stroke, the first check valve 4230 opens,
causing atmospheric air to enter the primary gas chamber 4250. The
intake of atmospheric air through the first check valve 4230
continues until the time the crank wheel 4500 has substantially
completed 180 degrees of rotation and the crank link 4400 is once
again horizontal. The volume of the gas in the primary gas chamber
4250 ranges from 6 to 9 cubic inches at standard temperature and
pressure conditions and, more preferably, 7 cubic inches.
Additionally, the crank wheel 4500 (coupled to the cam arrangement
4200) rotates the cam 4210 such that the cam arrangement 4200
enables opening and closing of the valve arrangement 4300. In the
present embodiment, the cam 4210 is coupled to the crank wheel in a
manner such that the two rotations of the crank wheel 4500 cause
one rotation of the cam 4210. The completion of one rotation of the
cam 2210 results in the opening of the valve arrangement 4300. The
crank wheel 4500 rotates in a clockwise direction thereby rotating
the cam 2210 in an anticlockwise direction.
Referring to FIG. 21, the first piston 220 is shown in the second
position (bottom dead center). In the second position, the crank
link 4400 is horizontal and the first check valve 4230 is closed.
The closing of the first check valve 4230 enables in accommodating
the gas in the primary gas chamber 4250 and prevents any exit of
gas from the primary gas chamber 4250. The further clockwise
rotation of the crank wheel 4500 (about 90 degrees) rotates the cam
4210 (about 45 degrees) in the anticlockwise direction.
Referring to the FIG. 22, the first piston 220 is shown in the
intermediate position. In the intermediate position, the first
piston 220 with the closed first check valve 4230 compresses the
gas in primary gas chamber 4250 such that the compression exponent
of the compressed gas within the primary gas chamber 4250 reaches
at least 1.05. The further clockwise rotation of the crank wheel
4500 rotates the cam 4210 in the anticlockwise direction.
Referring to the FIG. 23, a completion of the first stroke is
shown, when the first piston 220 is at first position. In the first
position when the first piston 220 reaches near to the separator
4270, the first piston 220 compresses the gas in the primary gas
chamber 4250 to an extent such that the second check valve 4232 of
separator 4270 opens for receiving the compressed gas into the
secondary gas chamber 4260. The compressed gas of the primary gas
chamber 4250 has the compression exponent of greater than 1.05.
Thereby, the compressed gas transferred to the secondary gas
chamber 4260 also has the compression exponent of greater than
1.05. In the completion of the first stroke, the crank wheel 4500
completes one rotation (360 degrees) and the cam 4210 completes
half a rotation (180 degrees).
Referring to FIGS. 24-28, the second stroke of the fastener driving
apparatus 4000 incorporating the cam arrangement 4200 and slider
crank arrangement 4100 is shown. More specifically, referring to
FIG. 24, a starting of the second stroke is shown, when the first
piston 220 is moving from the first position towards the second
position. The starting of the second stroke enables in the opening
of the first check valve 4230, at which moment the secondary valve
causing atmospheric air to enter the primary gas chamber 4250. The
intake of atmospheric air through the first check valve 4230
continues until the first piston 220 reaches the second position.
The crank wheel 4500 further rotates in a clockwise direction and
rotating the cam 4210 in an anticlockwise direction.
Referring to FIG. 25, the first piston 220 is shown in the second
position (bottom dead center). In the second position, the crank
link 4400 is horizontal and the first check valve 4230 is closed.
The closing of the first check valve 4230 enables in accommodating
the gas in the primary gas chamber 4250 and preventing any exit of
gas from the primary gas chamber 4250. The further clockwise
rotation of the crank wheel 4500 rotates the cam 4210 in the
anticlockwise direction.
Referring to the FIG. 26, the first piston 220 is shown in an
intermediate position. In the intermediate position, the first
piston 220 with the closed first check valve 4230 compresses the
gas in primary gas chamber 4250 such that the compression exponent
of the compressed gas within the primary gas chamber 4250 reaches
at least 1.05. The further clockwise rotation of the crank wheel
4500 rotates the cam 4210 in the anticlockwise direction.
Referring to the FIG. 27, the first piston 220 is shown in an
intermediate position near to the separator 4270 with a partial
opening of the valve arrangement 4300. Towards the first position,
when the first piston 220 reaches near to the separator 4270, the
first piston 220 compresses the gas in the primary gas chamber 4250
to an extent such that the second check valve 4232 of the separator
4270 opens and the cam arrangement 4200 enables in partial opening
of the valve arrangement 4300. In the intermediate position when
the valve arrangement 4300 is in the partial opened state, the cam
arrangement 4200 enables in opening the valve spool 320 of the
valve arrangement 4300. In this condition, the crank wheel 4500 is
about to complete two rotations (720 degrees) and the cam 4210 is
about to complete a one rotation (360 degrees).
The valve arrangement 4300 opens either when the gas pressure
inside the secondary gas chamber 4260 exceeds the maintaining force
of the valve spool 320 or when valve arrangement 4300 is made to
open by the cam arrangement 4200. In a preferred embodiment, the
valve arrangement 4300 is referred to as a snap acting valve in
which the valve spool has an opening speed of less then 20
milliseconds from initial cracking to greater than substantially 70
percent of full flow of the compressed gas. More specifically, the
opening time of the valve spool 320, i.e. the time from being
closed until the time the valve is at least 70 percent open, should
be less than 20 milliseconds (0.020 seconds). The valve spool 320
needs to open fully and quickly such that the energy of expansion
is not lost to the spool 320 and the valve retainers 340.
In the above mentioned condition, when the valve arrangement 4300
is partially opened, a further linear movement of the first piston
220 causes it to move towards the first position, i.e. towards the
separator 4270. In such a situation, the plurality of links 4220
coupled to the cam arrangement 4200 pulls the valve spool stem 332
thereby causing the valve spool 320 to move linearly inside the
central groove 312 of the valve body 310 in a manner such that, the
valve spool 320 opens the central hollow portion 242 and
substantially the gas passageway 360. The valve spool 320 opens the
central hollow portion 242, and the retention balls 344 cross a
tipping point 370, refer to FIG. 30. The tipping point 370, as used
herein, refers to a point of contact between the retention balls
344 and the valve spool 320, when the valve retainers 340 and the
retention balls 344 provide minimal resistance to the linear
movement of the valve spool 320, thereby resulting in an opening of
the gas passageway 360. At the tipping point 370, the retention
balls 344 provide minimal resistance to the linear movement of the
valve spool 320, thereby resulting in an opening of the gas
passageway 360. This enables the compressed gas within the
secondary gas chamber 4260 to be released into the second cylinder
400 through the valve arrangement 4300 and, more specifically,
through the gas passageway 360.
The compressed gas reaching the second cylinder starts expanding,
thereby applying pressure on the front face 422 of the second
piston 420 which causes the second piston 420 to move axially
towards the anvil drive bumper 460. The anvil 430 accordingly moves
axially into the fastener guide 530. The anvil retracting mechanism
450 gets compressed thereby storing energy into the anvil
retracting mechanism 450.
Referring to the FIG. 28, a completion of the second stroke is
shown; when the first piston 220 is at first position with a
complete opening of the valve arrangement 4300, (see FIG. 31). In
the completion of the second stroke, the first piston 220
compresses the gas in the primary gas chamber 4250 to an extent,
such that, the second check valve 4232 of separator 4270 remains
open and the cam arrangement 4200 enables in complete opening of
the valve arrangement 4300. In this condition, the crank wheel 4500
completes two rotations and the cam 4210 completes one rotation,
thereby opening the valve arrangement 4300 completely.
Upon completion of the second stroke (i.e. the first piston 220
reaching the first position) a maximum amount of compressed gas is
delivered to the second cylinder 400. The compressed gas in the
second cylinder 400 expands therein and applies pressure on the
second piston 420 causing it to move axially further towards the
anvil drive bumper 460. The anvil 430 axially moves further into
the fastener guide 530 and applies pressure on the fastener 500
disposed from the fastener feeder 550 into the fastener guide 530.
Due to the applied pressure by the anvil 430, the fastener 500 is
driven into the substrate 600, such that, the fastener driving
device 4000 completes the operational cycle (the first stroke and
the second stroke) of driving the single fastener 500 into the
substrate 600.
In yet another embodiment, the fastener driving apparatus 4000 may
be coupled with a clutch (not shown). Generally the operation
begins with the motor 20 starting to rotate slider crank
arrangement 4100, firing the valve arrangement 4300 and then
stopping. If a clutch is used, the motor 20 may be allowed to run
continuously. For example, when a nosepiece (i.e., a fastener guide
530) of the fastener driving apparatus 4000 is positioned against
the substrate 600, the motor 20 may be started. In this way, all
the energy needed is in the motor 20 before transferred to the
slider crank arrangement 4100. When the user pulls the start switch
(trigger), this engages the clutch which in turn engages the slider
crank arrangement 4100. Because the motor is not starting from a
"dead stop," energy can be extracted right away and much more
quickly.
Motors generally have the most power in the midrange of their
operating range of revolutions per minute (RPMs). These motors
deliver no power at the start (as they are not rotating yet) and
are less efficient at lower RPMs than at higher RPMs. If the
fastener driving apparatus 4000 is engaged in this fashion, the
fastener driving apparatus 4000 has a much more responsive feel.
For example, by using the fastener driving apparatus 4000 of the
present invention, the time from a trigger pull to driving an 18
gage fastener may be reduced from about 100 milliseconds to about
50 milliseconds while creating a much more responsive tool feel to
the professional user.
The foregoing descriptions of specific embodiments of the present
invention have been presented for purposes of illustration and
description. They are not intended to be exhaustive or to limit the
invention to the precise forms disclosed, and obviously many
modifications and variations are possible in light of the above
teaching. The embodiments were chosen and described in order to
best explain the principles of the invention and its practical
application, and to thereby enable others skilled in the art to
best utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated. It
is understood that various omissions and substitutions of
equivalents are contemplated as circumstances may suggest or render
expedient, but such are intended to cover the application or
implementation without departing from the spirit or scope of the
claims of the present invention.
* * * * *